About SimplyCalc
Last updated: May 2026
Why we built this
SimplyCalc was built out of a frustration shared by most people who have ever tried to work out a mortgage payment or take-home salary online: the best tools are buried inside financial product pages trying to sell you something, and the free ones are either inaccurate or surrounded by intrusive advertising that makes them harder to use.
We wanted a different kind of calculator site — one that gives accurate results, explains the methodology transparently, and does not have an agenda beyond being useful. Every calculation on SimplyCalc runs entirely in your browser. Nothing is sent to any server. We do not know what you calculated.
Who runs this
SimplyCalc is an independent project run by a small team with backgrounds in financial services, software development, and personal finance writing. Our contributors have experience in UK mortgage advice, tax planning, and financial data across the UK, EU, and US markets. We are not a regulated financial advisory firm and do not hold FCA or SEC authorisation — SimplyCalc is an educational and informational resource, not a substitute for professional advice.
We are contactable at hello@simplycalc.io. We respond to every message. If you find an error in a calculator or an article, please tell us — we correct mistakes promptly and publicly acknowledge them in the relevant page's methodology notes.
How we ensure accuracy
Every calculator uses current official rates and established formulae sourced directly from primary regulatory bodies:
- UK income tax and National Insurance — HMRC published thresholds for the current tax year, updated each April
- US federal income tax — IRS published tax brackets and standard deduction for the current filing year
- Mortgage calculations — standard amortisation formula, results cross-checked against major lender calculators
- BMI — WHO adult BMI classification thresholds (underweight <18.5, healthy 18.5–24.9, overweight 25–29.9, obese ≥30)
- Calorie needs — Mifflin-St Jeor TDEE formula, validated in a 2005 meta-analysis as the most accurate for most adults
- Body fat — US Navy circumference method (Hodgdon & Beckett, 1984)
- Currency rates — European Central Bank reference rates, updated daily via Frankfurter.app
- VAT — HMRC published VAT rate schedule
Calculator results are cross-verified against official sources before publication and reviewed when rates change. The date of last review is shown on each calculator page. Our full editorial process is described on the Editorial Standards page.
The calculators
SimplyCalc currently has seventeen free calculators: mortgage payments and full amortisation schedule, salary take-home pay for UK (2022/23–2025/26 historical), US (federal), Germany, Norway, Australia and Canada, BMI with WHO classification, body fat percentage via Navy method, daily calorie and TDEE needs, loan repayment with APR comparison, savings goal with compound interest, VAT add/remove, tip and bill splitting, retirement pot projection, debt payoff (snowball vs avalanche), inflation purchasing power, percentage calculation (three tools in one), live currency conversion, menstrual cycle and ovulation prediction, age to the day, and investment and ISA growth projection.
Each calculator is accompanied by explanatory content — the methodology used, a worked example with real numbers, what the result means practically, and what to do next. A calculator that only gives a number is only half useful.
How we make money
SimplyCalc is funded by advertising through Google AdSense. We do not accept affiliate arrangements with financial product providers, paid placements, or sponsored content. Our calculators and articles are not influenced by commercial relationships. The site will remain free.
We use Google Analytics to understand how the site is used. A consent banner appears on every page; if you decline, analytics does not run. Calculation data is never shared with advertisers — it stays in your browser.