Use the 28/36 rule: spend no more than 28% of gross income on housing, 36% on total debt.
Lenders typically require a DTI below 43% for conventional mortgages.
This calculator earns its keep at decision points: before accepting a loan, comparing investment platforms, or negotiating salary. The difference between the headline figure and the true cost or return is only visible with accurate arithmetic.
The most consequential mistake is comparing financial figures that are not on the same basis — gross versus net, before-tax versus after-tax, or nominal versus inflation-adjusted. Always check whether figures you are comparing use the same definition.
A first-time buyer models three scenarios before making an offer: 10%, 15%, and 20% deposit on a £280,000 property. The calculator shows exactly how the monthly payment and total interest cost change with each deposit level, making the decision visible rather than speculative.
Using the 28% rule with a 7% rate and 10% down, roughly $250,000–$300,000.
CalcPlanet – Free Online Calculators
725+ free calculators and 108 tools for math, money, health, and everyday life. Instant results, verified formulas, no sign-up.
By CalcPlanet Editorial · Reviewed against our Editorial Standards and Formula Sources.
CalcPlanet calculators are free, privacy-first, and formula-reviewed.
Editorial Standards · Formula Sources · Privacy · Terms · Contact
