Methodology

How Calc Angel calculators work, and the standards every tool on this site follows.

Formulas in the open

Every calculator page publishes the exact formula it uses, together with a worked example you can verify by hand. If you ever find a discrepancy between the published formula and the calculator's output, tell us — we treat that as a serious bug.

Server-side calculation

Calculations run on our servers rather than in your browser. That keeps results consistent across devices and embedded widgets, and lets us fix or improve a formula in one place, immediately, for everyone. Your inputs are transmitted to the server to calculate the result and are not intentionally retained — see the privacy policy for exactly what is and isn't kept.

Sources and verification

Statutory figures — tax bands, National Insurance thresholds, student-loan thresholds, statutory pay rates, bank holidays — are taken from the official sources listed in each calculator's Sources & verification section, together with the date the figures were last verified and the period they apply to. Who reviews them and on what schedule is set out in our editorial standards.

Stated assumptions

Simplified models are useful — hidden simplifications are dangerous. Each calculator lists its assumptions and limitations at the bottom of the page: what's modelled, what isn't, and where a professional's advice should replace a web tool.

Rates and thresholds

Where tools reference statutory figures (such as VAT rates or late-payment interest), defaults reflect the UK figures at the time of writing, and the fields remain editable so you can apply current or foreign rates. Always confirm material figures with the relevant authority.

Not professional advice

These tools are for information and estimation. They are not accounting, tax, legal or financial advice, and they don't replace a qualified professional who knows your circumstances.

Privacy of your figures

The numbers you type into a calculator are transmitted to the server to produce your result and are not intentionally retained. See the privacy policy for details.