Every calculator on PoundLogic has its own methodology page explaining the formula, the assumptions, and the data sources used. This page is the index.

Why we publish our methodology

Most online calculators are black boxes. You put numbers in, numbers come out, and you have no way to check whether the maths is right or what assumptions were made. We think that's the wrong model for a personal finance site. If our calculator disagrees with another one online, you should be able to work out which is wrong.

Every PoundLogic methodology page covers:

  • The formula
  • The assumptions
  • The data sources (with links to primary sources)
  • The limitations

Available methodology pages

Investing

Borrowing

Property

Tax

General assumptions

  • Tax year: current UK tax year (6 April to 5 April). Calculators are updated within two weeks of each 6 April and each Budget.
  • Currency: GBP (£). All figures are pounds sterling.
  • Geography: England, Wales and Northern Ireland rates apply by default unless otherwise stated. Scottish income tax and Scottish/Welsh stamp duty equivalents (LBTT, LTT) are handled in their own dedicated calculators.
  • Inflation: ignored unless explicitly modelled — figures are nominal (today's money).
  • Rounding: intermediate calculations use full precision; displayed figures are rounded to the nearest pound.

Primary data sources

If you think any figure on this site is wrong, email [email protected] — see our corrections policy.