Free Online Calculators
Free Online Calculators
Accurate, instant calculators for home buying, auto loans, investing, debt payoff, retirement planning, and fitness — no sign-up required.
Always Free
No paywalls, no subscriptions, no account needed.
Fully Private
All calculations run in your browser — nothing stored or sent.
No Sponsored Results
Our numbers come from the math, not from advertisers.
Mortgage Calculator
Monthly payment, amortization schedule, and loan comparison.
AutoAuto Loan Calculator
Monthly car payment with trade-in, taxes, and amortization.
FinanceCompound Interest
Investment growth with contributions, compounding, and inflation.
FinanceDebt Payoff Calculator
Avalanche vs snowball with total interest savings and timeline.
FinanceRetirement Savings
Nest egg target, Social Security, and drawdown modeling.
Mortgage Calculator
Monthly payment, total interest, amortization schedule, extra payments, and loan comparison.
Refinance Calculator
Calculate break-even point and savings from refinancing your existing mortgage.
Affordability Calculator
Find out how much home you can afford based on income, debts, and down payment.
Rent vs. Buy Calculator
Compare the true long-term cost of renting vs. buying a home in your market.
PMI Calculator
Calculate your private mortgage insurance cost and when it will be eliminated.
Home Equity (HELOC)
Calculate available equity and model HELOC or home equity loan payments.
Auto Loan Calculator
Monthly car payment with trade-in, taxes, fees, and amortization schedule.
Lease vs. Buy Calculator
Compare the true cost of leasing vs. buying a vehicle over time.
Car Affordability
Find out how much car you can afford based on income and monthly budget.
Total Cost of Ownership
5-year cost including depreciation, fuel, insurance, maintenance, and financing.
Gas vs. Electric
Calculate the break-even point and long-term savings of an EV vs. gas vehicle.
Compound Interest
Investment growth with monthly contributions, compounding frequency, and inflation adjustment.
Debt Payoff Calculator
Avalanche vs snowball strategy comparison with total interest savings and payoff timeline.
Retirement Savings
4% rule, nest egg target, Social Security, drawdown modeling, and on-track assessment.
BMI + Ideal Weight
Body mass index, ideal weight range, and health category assessment.
Calories & BMR
Daily calorie needs based on age, weight, height, activity level, and fitness goal.
Body Fat %
Estimate body fat percentage using Navy method measurements.
Macro Calculator
Daily protein, carb, and fat targets for your diet and fitness goals.
Free Calculators That Actually Explain the Math
numCruncher is a growing library of free online calculators for the financial and personal decisions that are hard to eyeball — what a mortgage really costs over 30 years, whether refinancing pays off, how fast a debt snowball clears, how much you need to retire, and what your daily calorie and macro targets should be. Every tool runs instantly in your browser with no sign-up, no paywall, and no data sent to a server. But a number on its own isn't very useful, so each calculator is paired with a plain-English guide that explains the formula behind it, walks through a worked example, and answers the questions people actually ask. The goal is to leave you understanding the result, not just staring at it.
How to Choose the Right Calculator
If you're weighing a home purchase, start with the affordability calculator to find your price range, then use the mortgage calculator to model the payment and the rent vs. buy calculator to sanity-check the decision against renting. Already own a home? The refinance calculator finds your break-even point and the home equity calculator shows what you can borrow against it. Car shoppers can pair the car affordability calculator with the total cost of ownership calculator to see past the sticker price. For long-term money questions, the compound interest and retirement calculators show how today's contributions grow over decades.
What We Cover
The library is organized into four areas. Home & Mortgage covers buying, financing, refinancing, PMI, and home equity. Auto covers loans, leasing versus buying, affordability, ownership costs, and the gas-versus-electric break-even. Finance & Investing covers compound growth, debt payoff strategies, and retirement planning. Health & Fitness covers BMI, body-fat percentage, calorie and BMR needs, and macronutrient targets. New calculators are added over time, and existing ones are updated as guidelines and best practices change.
How Our Calculators Work
Accuracy is the whole point. The financial tools use standard, published formulas — amortization for loans, compound-interest equations for investments, and widely used lender ratios like the 28/36 rule for affordability — so the results line up with what a bank or financial planner would calculate. The fitness tools use established equations such as Mifflin–St Jeor for metabolic rate and the U.S. Navy circumference method for body fat. Because everything is computed live in your browser from the numbers you enter, you can change an assumption and watch every downstream figure update instantly. That makes it easy to ask "what if" — what if rates drop half a point, what if I add $200 a month, what if I retire two years later — and see the answer immediately.
Private by Design
numCruncher never asks you to create an account, and the calculators don't transmit the numbers you type to any server. Your salary, your loan balance, your weight — it all stays on your screen and is gone when you close the tab. The calculators are free to use, and any guidance here is for general educational purposes; for decisions with real financial or health stakes, it's always worth confirming with a qualified professional who knows your full situation.