About Real Number Lab

Free calculators for big and complicated expenses, built on public data with every assumption in view.

Why we built this

Big purchases are usually sold on one number: the sticker price, the monthly payment, the rate. The real cost hides in everything else, like insurance, upkeep, fees, depreciation and the interest your cash could have earned. Real Number Lab adds all of it up so you can compare options on what they will actually cost you.

How we calculate

Public data where it exists. For example, the car calculators use US EPA fuel economy data from FuelEconomy.gov and owner complaint records from NHTSA.
Estimates are labeled. Where no free data exists, such as prices or insurance, we use clearly marked estimates. You can replace them with your own quotes.
Ranges, not false precision. Results include a plausible range that reruns the math with higher and lower costs.
Your inputs stay with you. The calculators run in your browser. There is no account and nothing to sign up for.

How we make money

Real Number Lab is free, with no ads or affiliate links today. If we add affiliate links later, for example to credit card offers, we will label them clearly, and they will not change how tools rank options.

Not financial advice

Our tools are for planning and education. They are not financial, tax or legal advice. Check real quotes and talk to a professional before big decisions.