Free Online Calculators
472+ interactive calculators for mortgage, retirement, loans, investing, taxes, and more. No sign-up required.
Calculator Categories
Choose a category or browse all 472+ calculators
Mortgage & Home
Mortgage payments, refinancing, rent vs buy
22 calculators
Retirement
401(k), IRA, retirement planning
17 calculators
Loans & Debt
Auto loans, student loans, debt payoff
12 calculators
Investment
Compound interest, ROI, savings goals
27 calculators
Tax
Income tax, payroll, self-employment
17 calculators
Auto
Auto loans, lease vs buy, fuel costs
15 calculators
Insurance
Life insurance needs, coverage
6 calculators
Business
Break-even, profit margin, cash flow
23 calculators
Credit Card
Payoff, balance transfer, rewards
3 calculators
Savings
Savings goals, emergency fund, CDs
10 calculators
Personal Finance
Net worth, budget, debt-to-income
14 calculators
Health
BMI, calories, HSA contributions
22 calculators
Real Estate
Cap rate, rental ROI, property analysis
9 calculators
Math
Percentages, algebra, geometry, and number tools
55 calculators
Statistics
Standard deviation, probability, z-scores, and data analysis
27 calculators
Fitness
Heart rate zones, pace, calories burned, and training tools
6 calculators
Construction
Square footage, concrete, roofing, flooring, and building materials
28 calculators
Physics
Ohms law, force, energy, motion, and electrical calculators
39 calculators
Chemistry
Molarity, pH, half-life, and chemical calculations
18 calculators
Everyday Life
Age, date, time, electricity, discounts, and school tools
14 calculators
Food & Cooking
Cooking conversions, recipe scaling, and food calculators
11 calculators
Ecology & Energy
Solar panels, carbon footprint, and green energy tools
5 calculators
Conversions
Temperature, length, weight, speed, and number base converters
7 calculators
Biology
Genetics, population growth, and biological calculations
5 calculators
Pets & Animals
Dog age, pet food, chocolate toxicity, and pet care calculators
6 calculators
Gardening
Mulch, soil, grass seed, and landscaping calculators
7 calculators
Clothing & Sizing
Shoe size, ring size, and clothing conversion calculators
5 calculators
Weather
Wind chill, heat index, dew point, and weather calculators
4 calculators
Technology
Password generator, IP subnet, bandwidth, and dev tools
9 calculators
Text & Word Tools
Word counter, character counter, and text utilities
4 calculators
Sports
Golf handicap, batting average, bowling score, and sports stats
5 calculators
Optics & Spectroscopy
Lens equations, diffraction, Cauchy/Sellmeier dispersion, spectroscopy tools
20 calculators
Embed Calculators on Your Site
Add interactive calculators to your website with a simple code snippet. Customize branding, colors, and choose which calculators to offer.
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Popular Calculators
Ten of the most-used calculators on CalcMountain
Mortgage Payment Calculator
Calculate your monthly mortgage payment including principal, interest, taxes, and insurance.
Compound Interest Calculator
See how your money grows over time with compound interest and regular contributions.
401(k) Calculator
Estimate your 401(k) balance at retirement with employer matching and investment growth.
Income Tax Estimator
Estimate your federal income tax using current brackets and deductions.
Auto Loan Calculator
Calculate your monthly car payment and total loan cost including trade-in and sales tax.
BMI Calculator
Calculate your Body Mass Index from height and weight.
Savings Goal Calculator
Find out how much to save each month to reach your financial goal.
ROI Calculator
Calculate return on investment including annualized returns and net gain.
Credit Card Payoff Calculator
Find out how long it will take to pay off your credit card and how much interest you will pay.
Calorie Calculator
Calculate daily calorie needs based on age, weight, height, and activity level.
What makes CalcMountain different
Most calculator sites are walls of ads with a tiny form squeezed in the middle. CalcMountain is built the opposite way: the calculator is the page, with real-time results, visual charts, and downloadable tables built in from the first load. No sign-up wall, no email capture, no paywall on the output.
Every calculator discloses its inputs and assumptions. Financial calculators follow conventions used by the U.S. CFPB, IRS, and SSA where relevant; health calculators use formulas recognized by the CDC, NIH, and peer-reviewed literature; conversions use SI-standard ratios. Results are estimates intended for planning and education — not professional financial, medical, legal, or engineering advice. Full methodology is on our about page.
If you run a site in a niche we cover, you can embed any of our calculators on your own pages with a small code snippet — keeping visitors on your site instead of sending them away. See pricing.