Free calculators,
with the math shown.
20 free calculators for mortgages, loans, savings, health and everyday math. Results update instantly as you type, and every page shows the formula, its sources and two worked examples.
- Free calculators
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- Unit tests
- 107
- Sign-ups
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Featured calculators
- Mortgage Payment CalculatorSee the full monthly cost of a home loan: principal and interest plus the escrow items most lenders collect with it.
- Compound Interest CalculatorSee how a starting balance and steady monthly deposits grow when interest earns interest.
- BMI CalculatorBody mass index compares weight with height. Enter yours to see your BMI, its CDC category and the weight range that counts as healthy for your height.
- Calorie Calculator (TDEE)Estimate total daily energy expenditure — the calories you burn on a typical day — and the intake that would hold, lower or raise your weight.
- Car Loan CalculatorWork out the monthly payment and the true total cost of a car before you sit down with the dealer.
- Retirement Savings CalculatorEstimate what your savings could grow to by retirement and what yearly income that might support, in today’s dollars.
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Calculators
20 calculators across mortgages, loans and savings, health and everyday math — each with its formula, cited sources and worked examples.
Mortgage & Housing
Monthly payments, schedules, payoff strategies, refinancing and how much home fits your budget.
- Mortgage Payment Calculator
- Amortization Schedule Calculator
- Extra Payment Calculator
- Biweekly Mortgage Payment Calculator
- Refinance Break-Even Calculator
- Home Affordability Calculator
Loans, Savings & Retirement
Interest, savings goals, retirement projections, credit card payoff and installment loans.
- Compound Interest Calculator
- Savings Goal Calculator
- Retirement Savings Calculator
- Credit Card Payoff Calculator
- Car Loan Calculator
- Loan Payment Calculator
Health & Fitness
Body measurements and daily energy and protein needs, using published clinical equations.
- BMI Calculator
- Calorie Calculator (TDEE)
- BMR Calculator
- Protein Intake Calculator
- Body Fat Calculator
- Ideal Weight Calculator
Everyday Math
Quick answers for dates, ages and percentages.
Why FlareLodge
Built like software, explained like a teacher.
Tested against published examples
Each formula is a small module with automated tests that reproduce worked examples from the CFPB, the Federal Reserve, the CDC and Excel’s own documentation.
The formula is on the page
Every calculator shows its equation, defines each variable, links its sources and walks through two examples with real numbers.
Private by design
Every tool runs in your browser. What you type is never sent to our servers, and there is nothing to sign up for.