Free UK calculators, converters and validators (tax, VAT, stamp duty, dates, units), read-only.
Connect Remote server
claude mcp add --transport http hopi https://mcp.hopi.co.uk/mcp{
"mcpServers": {
"hopi": {
"url": "https://mcp.hopi.co.uk/mcp"
}
}
}{
"servers": {
"hopi": {
"type": "http",
"url": "https://mcp.hopi.co.uk/mcp"
}
}
}Settings > Connectors > Add custom connector
URL: https://mcp.hopi.co.uk/mcpTools 80 found in our last check
hopi_add_working_daysAdd or subtract a number of working days (Monday to Friday) from a start date, optionally skipping England and Wales bank holidays. Dates use the YYYY-MM-DD format. Bank holiday data covers 2026 to 2028 only, so outside those years just weekends are skipped. Source: https://hopi…
hopi_age_calculatorWork out an exact age from a date of birth, as of today or an optional 'as of' date. Dates use the YYYY-MM-DD format. Returns the age in years, months and days, the total days lived, and the next birthday. Source: https://hopi.co.uk/age-calculator/
hopi_ai_prompt_builderBuild a well-structured prompt to paste into an AI chatbot or image generator. Give the task plus any of: the role the AI should take, background, audience, tone, format, length, things to avoid, an example of good output, and material to work on (for summarise, analyse and code…
hopi_alcohol_unit_calculatorWork out UK alcohol units in a drink from its ABV (percentage) and volume (millilitres), using units = ABV x ml / 1000. Optionally give the number of those drinks per week to get a weekly total compared against the NHS low risk guideline of 14 units a week. Source: https://hopi.…
hopi_alphabetical_orderSort the lines of a block of text into alphabetical order. Blank lines are dropped. Uses natural en-GB ordering so numbers within lines sort sensibly. Can sort ascending (A to Z) or descending (Z to A), and can ignore case. Source: https://hopi.co.uk/alphabetical-order/
hopi_angle_converterConvert an angle from one unit to another. Units: deg (degrees), rad (radians), grad (gradians), turn (full turns). Source: https://hopi.co.uk/angle-converter/
hopi_area_converterConvert an area from one unit to another. Units: sqm (square metres), sqft (square feet), sqyd (square yards), acre (acres), ha (hectares), sqkm (square kilometres), sqmi (square miles). Source: https://hopi.co.uk/area-converter/
hopi_aspect_ratio_calculatorAspect ratio helper. In 'simplify' mode, give width and height to get the simplified W:H ratio, decimal ratio and nearest common ratio. In 'solve' mode, give a ratio (ratioW:ratioH) plus one of width or height to get the missing side. Source: https://hopi.co.uk/aspect-ratio-calc…
hopi_average_calculatorWork out the mean, median, mode, sum, count, minimum and maximum of a list of numbers. Provide the numbers separated by spaces, commas, semicolons or new lines (type 1200 rather than 1,200, as commas are treated as separators). Source: https://hopi.co.uk/average-calculator/
hopi_base32_encoderEncode text to RFC 4648 Base32 or decode Base32 back to text. Encoding maps the UTF-8 bytes of the text into 5-bit groups using the alphabet A to Z then 2 to 7, padded to a multiple of 8 characters with equals signs. Decoding tolerates lowercase input and missing padding, and re…
hopi_base64Encode text to Base64, or decode a Base64 string back to text. UTF-8 safe, so accents and emoji survive the round trip. Returns the converted text or a clear error. Source: https://hopi.co.uk/base64/
hopi_bill_splitterSplit a restaurant bill between people. In 'itemised' mode, list each item with its amount and who shared it, then add an optional tip and service charge (both percentages applied to each person's own share). In 'even' mode, split one total evenly with an optional tip. Amounts i…
hopi_bingo_card_generatorGenerate one or more UK 90-ball bingo cards. Each card is a 3-row by 9-column grid holding 15 numbers, 5 per row, with each column drawing from its own decade (1 to 9, 10 to 19, and so on up to 80 to 90). Blank squares are null. Source: https://hopi.co.uk/bingo-card-generator/
hopi_birthday_magic_squareBuild Ramanujan's birthday magic square: a 4 x 4 grid whose top row is a date (day, month, first two digits of the year, last two digits) and whose rows, columns, diagonals and many other groups of four all add up to the same total. Pass date as YYYY-MM-DD (order dmy for day fir…
hopi_bitcoin_address_validatorCheck whether a Bitcoin address is valid by verifying its checksum and structure. Supports legacy Base58Check (P2PKH, P2SH) and Bech32/Bech32m SegWit and Taproot addresses, on mainnet and testnet. Does not query the blockchain or check balances. Source: https://hopi.co.uk/bitcoi…
hopi_bmi_calculatorWork out body mass index (BMI) from height and weight, with the NHS weight category. Use units 'metric' with heightCm and weightKg, or 'imperial' with heightInches and weightPounds. BMI = weight in kg / (height in metres squared). Source: https://hopi.co.uk/bmi-calculator/
hopi_body_fat_calculatorEstimate body fat percentage using the US Navy tape method from a few measurements. For males give height, neck and waist; for females give height, neck, waist and hip. Use units 'metric' (centimetres) or 'imperial' (inches). Optionally give weight (kg for metric, pounds for imp…
hopi_caesar_cipherEncode or decode text with a Caesar shift cipher. Each letter is moved along the alphabet by the shift amount; a shift of 13 is ROT13. Only A to Z letters are changed, everything else is left as is. Decoding applies the opposite shift. Source: https://hopi.co.uk/caesar-cipher/
hopi_cagr_calculatorWork out the compound annual growth rate (CAGR) that takes a starting value to an ending value over a number of years. Returns the annual rate, the total growth and the growth multiple. Source: https://hopi.co.uk/cagr-calculator/
hopi_calories_to_kjConvert food energy between kilocalories (kcal) and kilojoules (kJ) using the exact factor 1 kcal = 4.184 kJ. Give an amount and its unit ('kcal' or 'kj'); returns both values. Source: https://hopi.co.uk/calories-to-kj/
hopi_captcha_embed_code_generatorGenerate the embed code for a CAPTCHA on a web form plus the server code that checks the token. Providers: turnstile (Cloudflare Turnstile), hcaptcha, recaptcha2 (reCAPTCHA v2 checkbox), recaptcha3 (reCAPTCHA v3 score) and altcha (self-hosted proof of work, no account). Servers:…
hopi_case_converterConvert text to a different letter case. 'upper' is UPPERCASE, 'lower' is lowercase, 'title' capitalises the first letter of each word, and 'sentence' capitalises the first letter of each sentence. Source: https://hopi.co.uk/case-converter/
hopi_cat_age_calculatorConvert a cat's age in years to an approximate human age, using the standard 15, 24, then 4 a year chart. Returns the human-equivalent age and the cat's life stage. Source: https://hopi.co.uk/cat-age-calculator/
hopi_celsius_to_fahrenheitConvert a temperature between Celsius and Fahrenheit. Also returns Kelvin. Set direction to 'c-to-f' or 'f-to-c'. Source: https://hopi.co.uk/celsius-to-fahrenheit/
hopi_character_counterCount the characters in a block of text, including a count with spaces removed, the word count, how many SMS messages it would take to send, and the Twitter/X characters remaining out of 280. Source: https://hopi.co.uk/character-counter/
hopi_cipher_identifierIdentify what encoding or classical cipher a piece of text probably is (Base64, Base32, hex, binary, octal or decimal ASCII, URL encoding, HTML entities, Morse, Caesar or ROT-N, Atbash, reversed text) or recognise it as a UUID, IPv4 address, Unix timestamp, JWT or hash digest. R…
hopi_cm_to_feetConvert a height between centimetres and feet/inches. Direction 'cm-to-feet' takes cm and returns feet and inches. Direction 'feet-to-cm' takes feet and inches and returns cm. Source: https://hopi.co.uk/cm-to-feet/
hopi_cmyk_to_rgbConvert print CMYK values (each 0 to 100) to on-screen RGB and hex, or convert RGB (each 0 to 255) the other way to CMYK. Uses the standard device-independent conversion. Source: https://hopi.co.uk/cmyk-to-rgb/
hopi_coin_flipFlip a fair coin one or more times. Returns each result plus a tally of heads and tails. Source: https://hopi.co.uk/coin-flip/
hopi_collatz_conjecture_calculatorRun the Collatz (3n + 1) rule on a positive whole number of up to 1,000 digits: halve it when even, treble it and add 1 when odd, until it reaches 1. Returns the total steps, odd and even step counts, the highest value reached and the step it was reached at, and the path itself…
hopi_colour_name_finderFind the named CSS colour that exactly or most closely matches a hex code, using straight-line distance in RGB space across the 148 named CSS colours. Source: https://hopi.co.uk/colour-name-finder/
hopi_colour_palette_generatorGenerate a five-swatch colour palette from a base hex colour using a chosen scheme: analogous, complementary, triadic or mixed. Supporting swatches carry a small random variation, so results vary slightly each call. Source: https://hopi.co.uk/colour-palette-generator/
hopi_colour_pickerGiven a six-digit hex colour code (with or without a leading #), return its hex, RGB and HSL values. Source: https://hopi.co.uk/colour-picker/
hopi_colour_shades_generatorFrom a base hex colour, generate five progressively lighter tints (mixed towards white) and five progressively darker shades (mixed towards black), each in five equal steps of one sixth. Source: https://hopi.co.uk/colour-shades-generator/
hopi_combination_generatorList every way to choose r items from a list, ignoring order (combinations). Returns the total count and the combinations themselves (the first 5000). Source: https://hopi.co.uk/combination-generator/
hopi_compound_interest_calculatorProject savings growth from a starting deposit plus a regular monthly contribution, compounded monthly with contributions added at the end of each month. Returns the final balance, total paid in and interest earned. Amounts in GBP, rate is the annual rate as a percentage. Source…
hopi_contrast_checkerWork out the WCAG contrast ratio between a foreground (text) colour and a background colour, both as hex codes, and report whether it passes AA and AAA for normal and large text. Source: https://hopi.co.uk/contrast-checker/
hopi_cron_expression_parserTranslate a standard five-field cron expression (minute, hour, day-of-month, month, day-of-week) into plain English. Understands stars, steps, ranges, lists and month and day names, plus shortcuts like @daily and @hourly. Source: https://hopi.co.uk/cron-expression-parser/
hopi_crypto_profit_calculatorWork out profit or loss on a crypto trade from buy price, quantity and an optional per-side fee percentage. Returns breakeven price always, and profit, return percentage and total fees once a sell price is given. All figures are treated as GBP. Source: https://hopi.co.uk/crypto-…
hopi_css_gradient_generatorBuild a ready-to-use CSS gradient from two colours. Choose a linear gradient with an angle in degrees, or a radial gradient. Returns the gradient value and a full background declaration. Source: https://hopi.co.uk/css-gradient-generator/
hopi_css_minifierMinify CSS by removing comments and needless whitespace, while preserving quoted strings and the spaces inside calc() expressions. Returns the minified CSS with before and after byte sizes. Source: https://hopi.co.uk/css-minifier/
hopi_csv_to_jsonConvert CSV text into a JSON array, following standard CSV quoting rules for embedded commas, quotes and line breaks. With headers on, the first row becomes object keys; with headers off, each row is an array of strings. Source: https://hopi.co.uk/csv-to-json/
hopi_cups_to_gramsConvert US cups of a common baking ingredient to grams (approximate). Ingredients: flour (plain flour), caster (caster sugar), brown (packed brown sugar), butter, cocoa (cocoa powder), oats, rice (uncooked rice), icing (icing sugar). Source: https://hopi.co.uk/cups-to-grams/
hopi_currency_converterConvert an amount of money from one currency to another using Hopi's live mid-market exchange rates (updated hourly, 150+ currencies). Use ISO 4217 codes such as GBP, EUR, USD, JPY. Source: https://hopi.co.uk/currency-converter/
hopi_data_size_converterConvert a digital storage size between units. Units: B (bytes), KB, MB, GB, TB. By default 1 KB = 1000 bytes (decimal, as storage is sold). Set binary to true for 1 KB = 1024 bytes (as Windows reports drive sizes). Source: https://hopi.co.uk/data-size-converter/
hopi_date_calculatorAdd or subtract a number of days, weeks, months or years from a date. Dates use the YYYY-MM-DD format. Months and years are clamped to the last day of the target month where needed. Returns the resulting date. Source: https://hopi.co.uk/date-calculator/
hopi_day_of_week_calculatorFind which day of the week a given date falls on. Dates use the YYYY-MM-DD format. Also reports which weekday that same day and month falls on in the current year. Source: https://hopi.co.uk/day-of-week-calculator/
hopi_day_rate_calculatorConvert between a contractor day rate and an annual salary equivalent using a chosen number of billable working days per year (default 220). Mode 'to_salary' turns a day rate into yearly, monthly and weekly figures; mode 'to_rate' turns a salary into a day rate. Gross amounts in…
hopi_days_between_datesCount the number of days between two dates, with the total also shown in weeks and in weekdays (Monday to Friday). Dates use the YYYY-MM-DD format. Set inclusive to true to count both end days. Source: https://hopi.co.uk/days-between-dates/
hopi_days_until_christmasCount the number of sleeps until the next Christmas Day (25 December). Uses today's date by default, or an optional 'from' date in YYYY-MM-DD format. Source: https://hopi.co.uk/days-until-christmas/
hopi_dca_calculatorWork out the average cost basis across a series of pound-cost-averaged buys. Each buy is an amount of money spent and the price paid per unit. Returns total invested, coins acquired and average cost, plus current value and unrealised profit or loss if a current price is given. F…
hopi_dice_rollerRoll one or more dice with a given number of sides. Returns each die result plus the total, highest and lowest. Source: https://hopi.co.uk/dice-roller/
hopi_diff_checkerCompare two texts line by line using a longest common subsequence diff, and report which lines were added and which were removed. An edited line shows as one removed line plus one added line. Comparison is exact, including spaces and case. Source: https://hopi.co.uk/diff-checker/
hopi_discount_calculatorWork out a discount and sale price. Mode 'pct': a percentage off a price. Mode 'fixed': a fixed pound amount off a price. Mode 'find': the discount percentage from an original price and a final price. All money figures are in pounds. Source: https://hopi.co.uk/discount-calculato…
hopi_dog_age_calculatorConvert a dog's age in years to an approximate human age, using the standard veterinary chart. The later rate depends on the dog's size: small, medium or large. Returns the human-equivalent age. Source: https://hopi.co.uk/dog-age-calculator/
hopi_download_time_calculatorEstimate how long a download takes. Give a file size with its unit (MB, GB, TB) and a connection speed with its unit (Mbps or Gbps in bits per second, or MBps in bytes per second). Returns a human-readable duration and the time in seconds. Source: https://hopi.co.uk/download-tim…
hopi_due_date_calculatorEstimate a pregnancy due date from the first day of the last menstrual period (LMP) and cycle length. Method: adjust the LMP by (cycle - 28) days, then add 280 days for the due date. Also returns the dates the second and third trimesters begin (LMP-adjusted + 84 and + 182 days).…
hopi_dummy_data_generatorGenerate fake but safe UK test records. Phone numbers come from Ofcom's reserved drama ranges and emails use RFC 2606 example domains, so no record can reach a real person. Returns an array of records, plus CSV text. Source: https://hopi.co.uk/dummy-data-generator/
hopi_email_header_analyserAnalyse raw email headers (the full source from Show original or View message source) without any network call: lists every Received hop in delivery order with host, IP, time and delay between hops; extracts From, Reply-To, Return-Path, Subject, Date, Message-ID and mailer; read…
hopi_email_link_generatorBuild a correctly percent-encoded mailto link from to, cc, bcc, subject and body fields, plus a ready to paste HTML anchor snippet. Spaces are encoded as %20 and line breaks as %0D%0A, as the mailto standard expects. Source: https://hopi.co.uk/email-link-generator/
hopi_emoji_removerRemove emoji from a block of text, leaving the words and normal punctuation intact. Joined emoji sequences (such as a family or a flag) count as a single emoji. The copyright, registered and trademark symbols are kept. Returns the cleaned text and how many emoji were removed. So…
hopi_energy_cost_calculatorWork out the running cost of an electrical appliance from its power in watts, hours used per day and your electricity unit price in pence per kWh. Returns daily, weekly, monthly and yearly cost plus kWh used. Costs in GBP. Source: https://hopi.co.uk/energy-cost-calculator/
hopi_env_to_jsonConvert between a .env file and a JSON object. In env-to-json mode, each line is split on its first equals sign into a key and value, blank and commented lines are skipped, a leading export is removed, and matching surrounding quotes are stripped (double-quoted values also unesc…
hopi_eth_address_checksumValidate an Ethereum address's EIP-55 capitalisation checksum and return the correctly checksummed form. Reports whether the input is already checksummed, lacks a checksum (all one case), or fails the checksum. Uses keccak-256 exactly as EIP-55 specifies. Source: https://hopi.co…
hopi_eth_unit_converterConvert an amount given in wei, gwei or ETH into all three units, using exact 18-decimal integer maths (no floating point error). 1 ETH is 1e18 wei; 1 gwei is 1e9 wei. Source: https://hopi.co.uk/eth-unit-converter/
hopi_euromillions_generatorGenerate random EuroMillions lines. Each line has 5 main numbers from 1 to 50 and 2 Lucky Stars from 1 to 12. Source: https://hopi.co.uk/euromillions-generator/
hopi_event_wine_calculatorWork out how many bottles of red, white and Champagne to buy for an event, from the number of guests and glasses per guest. Ticking different wines splits a colour into one wine per glass, each poured once for every guest. Source: https://hopi.co.uk/event-wine-calculator/
hopi_fortune_cookieCrack open a virtual fortune cookie and receive a random cheerful fortune. Returns the fortune. Source: https://hopi.co.uk/fortune-cookie/
hopi_fraction_calculatorAdd, subtract, multiply or divide two fractions, giving the simplified result, a mixed number where relevant, and the decimal value. Each fraction is a numerator over a denominator, all whole numbers (numerators may be negative). Source: https://hopi.co.uk/fraction-calculator/
hopi_fraction_to_decimalConvert between fractions and decimals. Mode 'toDecimal': give a numerator and denominator (whole numbers) to get the decimal and percentage. Mode 'toFraction': give a decimal to get the closest simplified fraction (denominator up to 10,000), noting whether it is exact. Source:…
hopi_fuel_cost_calculatorEstimate the fuel cost of a journey from the distance in miles, the car's fuel economy in miles per gallon (UK gallon) and the pump price in pence per litre. Optionally double it for a return trip and split between passengers. Returns total cost, litres used and cost per person.…
hopi_gold_coin_value_calculatorWork out the gold content and melt value in pounds of a gold coin or bar (sovereigns, Britannias, Krugerrands and other 1 oz coins, or bars from 1 g to 1 kg) at Hopi's live mid-market gold price (updated hourly). With a dealer's price and buy-back it returns the premium over mel…
hopi_gold_return_calculatorWork out the return on gold bought in the past (sovereigns, Britannias, Krugerrands and other 1 oz coins, bars from 1 g to 1 kg, or any weight and fineness), before and after UK inflation. Values the gold at its melt value at Hopi's live mid-market gold price (updated hourly), t…
hopi_gold_value_calculatorWork out the melt (scrap) value in pounds of gold jewellery or any gold item from its weight and carat or fineness, at Hopi's live mid-market gold price (updated hourly). Optionally compares a buyer's offer with the melt value. Source: https://hopi.co.uk/gold-value-calculator/
hopi_hash_generatorCompute the SHA-256, SHA-1 or SHA-512 hash of a piece of text and return the hex digest. Uses WebCrypto on Hopi's server. SHA-1 is included for compatibility with older systems only and should not be used for anything new. Source: https://hopi.co.uk/hash-generator/
hopi_hash_identifierIdentify the most likely algorithms behind a hash string from its length, character set and any prefix. Covers MD5, NTLM, MD4, SHA-1, RIPEMD-160, SHA-224/256/384/512, the SHA3 family, CRC32, bcrypt, Argon2, sha512crypt, sha256crypt and md5crypt, plus Base64 length hints. A hash…
hopi_heart_rate_zonesEstimate maximum heart rate and five training zones (bpm) from age. Max HR = 220 - age. Method 'max' uses percentages of max HR (50-60, 60-70, 70-80, 80-90, 90-100%). Method 'karvonen' uses heart rate reserve and needs restingHeartRate: zone = (maxHR - resting) x intensity + res…
hopi_hex_to_rgbConvert a hex colour code (3, 6 or 8 digits, with or without a leading #) to its RGB and HSL values. Source: https://hopi.co.uk/hex-to-rgb/
hopi_hidden_character_checkerScan text for hidden and suspicious Unicode characters and return a cleaned copy. Finds zero-width space, joiner and non-joiner (U+200B to U+200D), word joiner U+2060, byte order mark U+FEFF, soft hyphen U+00AD, no-break and narrow no-break spaces, hair and thin spaces, bidirect…
hopi_holiday_entitlement_calculatorWork out UK statutory paid holiday entitlement from the number of days worked per week, using 5.6 weeks a year capped at the statutory 28 days. Optionally scale to a part-year by the number of months worked. Returns entitlement in days and weeks. Source: https://hopi.co.uk/holid…
Details
| Endpoint | https://mcp.hopi.co.uk/mcp (Streamable HTTP) |
| First published | 20 Sep 2026 |
| Last updated | 20 Sep 2026 |
| Registry name | uk.co.hopi/hopi |
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