How we calculate
Last updated: October 20, 2026
Every LeaseMathHub calculator follows the same rules, so you can trust — and check — the numbers.
Our principles
- Standard formulas only. Each calculator uses the formula lenders, dealers or tax authorities use, and shows it on the page with a worked example you can redo by hand.
- Checked by hand. Before publishing, every calculator is tested against hand-calculated examples (they are written as comments in our code) and against edge cases such as 0% interest or very long terms.
- Official sources for rates and taxes. Tax rules and official rates (for example the IRS mileage rates, German vehicle tax or company-car rules, Italian road tax) come from the law or the authority that publishes them, and are linked on each page.
- Estimates, clearly labelled. Results are estimates for planning. Lenders round differently, and local taxes and fees vary. Your contract or tax notice always wins.
- Private by design. All calculations run in your browser. We never receive the numbers you type.
Key formulas
Lease (US): payment = (cap cost − residual) ÷ term + (cap cost + residual) × money factor (+ tax)
APR = money factor × 2,400
Loan: payment = principal × r ÷ (1 − (1 + r)^−n), r = APR ÷ 12
Fuel: cost = distance ÷ mpg × price or distance × L/100 km ÷ 100 × price
Tires: diameter = rim × 25.4 + 2 × width × aspect ÷ 100
Power: 1 kW = 1.34102 hp = 1.35962 PS
Updates
Rates that change every year (such as mileage rates and tax tables) are reviewed at least once a year and whenever the law changes. Each page shows the date it was last updated.
Found a mistake?
Please tell us with the numbers you used. We correct confirmed errors quickly.
Who is behind the site
LeaseMathHub is built and maintained by Jose Luis, a software developer based in Spain. More about the site.