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Calculators and converters that get the numbers right

129 professional tools for money, tax, health, maths, dates, text, code and SEO — with country-specific rules for the UK, Germany, Turkey and beyond.

Free, unlimited use
Nothing stored on our servers
3 languages, local rules

Browse by category

Twelve focused collections, each maintained with the rules and rates of the countries we serve.

Finance & tax Loans, mortgages, savings, tax and VAT 18 tools Business & pricing Margins, invoices, payroll and break-even 9 tools Health & fitness BMI, calories, macros, pregnancy and training 12 tools Maths & numbers Percentages, statistics, fractions and algebra 12 tools Unit converters Length, weight, temperature, data and more 14 tools Date & time Age, durations, working days and time zones 8 tools Text & writing Counting, cleaning, formatting and analysing text 10 tools Developer tools JSON, encoding, regex, hashes and formats 15 tools SEO & web Meta tags, schema, sitemaps and link tools 9 tools Colour & design Colour conversion, contrast, gradients and CSS 5 tools Security & privacy Passwords, hashes, encoding and validation 10 tools Study & school Grades, GPA, exam scores and study planning 7 tools

Most used tools

What visitors reach for most this month.

UK Take-Home Pay Calculator Calculate your UK net salary after income tax, National Insurance and student loan deductions for the… Finance & tax United Kingdom VAT Calculator Add or remove VAT from any amount. Supports all EU and UK VAT rates with automatic country selection… Finance & tax United Kingdom Germany Turkey France Spain Italy Netherlands Portugal UK Stamp Duty Calculator Calculate Stamp Duty Land Tax for England and Northern Ireland. Covers first-time buyers, second homes… Finance & tax United Kingdom IBAN Validator Validate IBAN numbers using the official check-digit algorithm. Shows country, bank identifier and… Security & privacy United Kingdom Germany Turkey France Spain Italy Netherlands Portugal BMI Calculator Calculate your Body Mass Index from height and weight. Shows BMI category, healthy weight range and… Health & fitness JSON Formatter Format, validate and minify JSON. Options for indent size, key sorting and Unicode escaping. Instant… Developer tools Mortgage Calculator Calculate monthly mortgage repayments, total interest and view a full amortisation schedule. Supports… Finance & tax Calorie Calculator Estimate daily calorie needs using Mifflin-St Jeor or Harris-Benedict equations. Adjusts for activity… Health & fitness Word Counter Count words, characters, sentences, paragraphs and estimate reading time. Useful for SEO content… Text & writing National ID Validator Validate national identification numbers for multiple countries using their official checksum… Security & privacy Spain Portugal Netherlands France Germany United Kingdom Percentage Calculator Calculate percentages in three modes: what is X% of Y, what percentage is X of Y, and find the total… Maths & numbers Age Calculator Calculate exact age in years, months and days from a birth date. Also shows total days lived, upcoming… Date & time

Browse all 129 tools

Built for United Kingdom

Tax bands, allowances and identifiers specific to United Kingdom — reviewed against official sources.

United Kingdom tools

Explore the catalogue

A quick look inside the biggest collections.

Guides and explainers

Plain-language background so you know what the numbers mean.

2026-03-15 Technical SEO Checklist — Meta Tags, Robots, Hreflang & Structured Data A hands-on checklist for technical SEO: meta tags, robots.txt, XML sitemaps, hreflang, canonical URLs, structured data and page-speed fundamentals. Read guide 2026-03-01 Compound Interest — How Your Money Grows (or Costs) Exponentially Understand compound interest, compounding frequency, the Rule of 72 and how to harness exponential growth for savings or avoid it on debt. Read guide 2026-02-10 BMI and Body Composition — What the Numbers Really Mean Go beyond BMI: understand body fat percentage, lean mass, waist-to-height ratio and why context matters more than a single number. Read guide

Why people trust Ayduke

Boring engineering, carefully documented rules and no dark patterns.

Documented accuracy

Every tax and rate table cites its source and shows the tax year it applies to.

Private by design

Calculations run on our server for one request and are never stored or profiled.

Instant results

Pages weigh a fraction of a typical calculator site and work on any device.

Genuinely localised

Not machine-translated wrappers: each language gets the tools that country actually needs.

Frequently asked questions

Is Ayduke really free?

Yes. Every tool is free with no registration, no usage caps and no paywalled results. The site is funded by advertising, which is clearly labelled and kept away from the calculators themselves.

Do you store the numbers I enter?

No. Inputs are processed for the length of one request and then discarded. We do not build profiles, and no calculation history is written to disk.

How current are the tax rates and allowances?

Country-specific tools show the tax year they use and link to the official source (HMRC, Bundesfinanzministerium, GİB and equivalents). We review them at the start of each tax year and after in-year changes.

Which languages are supported?

English, German, Turkish, French, Spanish, Italian, Dutch and Portuguese. Each language shows only the tools that have been translated and localised for it, so you never land on a half-English page.

Can I use the results for tax returns or medical decisions?

Use them as a well-documented estimate. They are not a substitute for a qualified accountant, adviser or clinician — see our disclaimer for details.