Free Online Tools

Calculators that actually help

Science-based health, fitness, and finance calculators. Fast, free, no signup required.

Sleep Calculator

Find the best bedtime or wake-up time based on 90-minute sleep cycles. Includes nap calculator.

Pregnancy Due Date Calculator

Estimate your baby's due date based on last period or conception date. Includes trimester timeline and weekly milestones.

Ovulation Calculator

Predict your fertile window, ovulation date, and best days to conceive. Includes 6-month calendar forecast.

Blood Alcohol Calculator

Estimate your BAC level based on drinks, weight, and time. See how long until you're sober.

Estimate your one-rep max for any lift. Includes training load percentages for every rep range.

Compound Interest Calculator

See how your money grows over time with interactive charts. Supports daily, monthly, quarterly compounding.

Macro Calculator

Get personalized daily protein, carb, and fat targets based on your body and fitness goals.

Target Heart Rate Calculator

Find your 5 training zones for fat burning, cardio, and peak performance using the Karvonen formula.

Credit Card Payoff Calculator

See how long to pay off credit card debt. Compare minimum vs fixed payments and total interest cost.

Salary to Hourly Calculator

Convert annual salary to hourly rate and back. Includes estimated take-home after taxes.

Rent vs. Buy Calculator

Compare the true cost of renting vs buying a home. See your break-even point and equity growth.

50/30/20 Budget Calculator

Split your income into needs, wants, and savings using the most popular budgeting rule.

Body Fat Calculator

Estimate body fat percentage using the U.S. Navy method. Just needs a tape measure.

Ideal Weight Calculator

Find your healthy weight range using 4 proven formulas: Devine, Robinson, Miller, and Hamwi.

Water Intake Calculator

Calculate daily hydration needs based on weight, activity, and climate. Includes a drinking schedule.

TDEE Calculator

Find your Total Daily Energy Expenditure — how many calories you actually burn per day. The key number for any diet.

Calorie Deficit Calculator

Plan your weight loss timeline. See daily calorie targets and week-by-week projections to your goal weight.

Calculate basal metabolic rate with Mifflin-St Jeor and Harris-Benedict. Includes TDEE and calorie targets.

Mortgage Payoff Calculator

See how extra monthly payments cut years off your mortgage and save thousands in interest. Includes full amortization schedule.

Car Loan Payoff Calculator

See how extra payments pay off your auto loan faster and cut total interest. Includes a full payment schedule.

Debt Payoff Calculator

Pay off all your debts using the snowball or avalanche method. See your debt-free date and total interest saved.

401(k) Calculator

Estimate your 401(k) balance at retirement with employer match and growth. See the impact of contributing more.

Roth IRA Calculator

Estimate your tax-free retirement balance, check contribution limits and income eligibility, and see decades of compound growth.

Retirement Calculator

Project your nest egg at retirement and estimate how long it will last based on your monthly spending.

Net Worth Calculator

Add your assets and debts to find your net worth, see your asset breakdown, and track your financial progress.

Why FitCalcTools?

Every calculator on this site is built with one goal: give you accurate, actionable results in seconds — no accounts, no paywalls, no bloated apps. Each tool uses peer-reviewed formulas (Mifflin-St Jeor, U.S. Navy body fat method, standard compound interest equations) and includes the scientific context you need to actually understand and use the results.

Whether you're optimizing your sleep schedule, planning your nutrition, tracking body composition, or projecting investment growth, FitCalcTools gives you the answer fast and explains the "why" behind it.