Methodology & Sources

Every calculator here uses publicly verifiable rules. Here's the logic, the assumptions, and the cross-check.

By · Updated · Methodology

Income tax & National Insurance

Calculations use the UK Government's published tax bands for the 2024/25 tax year:

  • Personal Allowance: £12,570 (tapered by £1 for every £2 earned above £100,000 until fully withdrawn at £125,140).
  • Basic rate: 20% on £12,571–£50,270.
  • Higher rate: 40% on £50,271–£125,140.
  • Additional rate: 45% above £125,140.
  • Employee NI: 8% on £12,571–£50,270; 2% above.

Cross-check: gov.uk/income-tax-rates.

Stamp Duty Land Tax

Uses the slice-based SDLT bands for main-residence purchases in England and Northern Ireland. First-time buyer relief applies only when the purchase price is £625,000 or below and all buyers are first-time buyers.

Cross-check: gov.uk/stamp-duty-land-tax. Scotland uses Land and Buildings Transaction Tax (LBTT); Wales uses Land Transaction Tax (LTT).

Compound interest

Uses the standard compound interest formula A = P × (1 + r/n)^(n·t), compounded monthly (n = 12). When a fixed annual rate is assumed for illustrative purposes, it is labelled on the page. Real-world returns vary.

VAT

Standard UK VAT rate of 20% applied to net figures to produce gross, or divided out of gross figures (gross ÷ 1.2). Registration threshold of £90,000 rolling 12-month taxable turnover.

Cost-of-living city pages

City council tax Band D figures are taken from each local authority's 2024/25 budget notice. Rent figures are median 1-bed asking rents aggregated from ONS Private Rental Market statistics and major rental platforms. Median salary figures are from ONS ASHE 2024. Figures are indicative and rounded — always verify with your local council and a current property search before making a decision.

What we don't claim

  • This is not personalised financial advice. For decisions with legal or tax consequences, consult a qualified accountant or regulated financial adviser.
  • Rates, allowances, and bands change each tax year. We update at the start of each new tax year; check the "updated" date on individual pages.
  • Regional variations (Scotland, Wales, NI) are noted where relevant but some calculators default to England/NI rules.

Corrections

Found an error? Email hello@oddlyuseful.xyz. Corrections are dated and linked from the affected page.