Calculator Methodology

Our calculators are designed around clearly stated mathematical formulas and user-entered assumptions. We show the major inputs, the resulting estimate and relevant limitations so visitors can understand what the number means.

Calculation approach

Where a standard mathematical formula is used, the page explains the variables and applies the formula consistently. Results are rounded for display.

Assumptions

Some calculators use an assumed interest rate, return or compounding convention. These assumptions are not guarantees and can be changed by the visitor where the calculator provides an input.

Verification

We aim to review calculation logic and explanatory content as the website evolves. Rate-sensitive or rule-sensitive calculations should always be compared with current official information.

Limitations

A calculator is a planning aid, not a substitute for a lender quote, official tax computation, payroll statement, investment statement or professional advice.

Last reviewed: August 2026.

Calculation testing

Calculator logic should be tested with normal values, zero-rate cases where relevant, small and large inputs, and boundary conditions. Display rounding should not change the underlying calculation.

Source hierarchy

For rule-sensitive subjects such as tax, employment or government savings schemes, official government or institutional information should take priority over secondary summaries when verifying current rules.