かしこい・お金・の・決断Make smarter money decisions.
Precise calculators and calmly-written guides for UK mortgages, tax, pensions and savings — built with British rigour, German engineering and Japanese restraint.
Calculators
Four tools · Updated for 2026/27Mortgage
Calculator.
Calculate monthly payments, total interest, and affordability for UK mortgages.
Avg. monthly · £300k @ 5.5%
Total interest · 25-yr term
Tax
Calculator.
Estimate income tax, National Insurance, and take-home pay for UK taxpayers.
Savings
Calculator.
Plan your savings goals with compound interest calculations for UK accounts.
Stamp Duty
Calculator.
Calculate stamp duty land tax for UK property purchases.
By the numbers
Twelve months · 2025UK households used a calculator on this site last year
In mortgage interest avoided through overpayment modelling
Of figures verified against HMRC and Bank of England sources
No paywall, no account required, no data sold
“A calculator is the cheapest financial advice you'll ever read. We just make sure it tells the truth.
Should you fix for two years or five?
With base rates wobbling either side of 4.5%, the case for a 5-year fix is back — but only for the right kind of borrower.
Read the full piece