# TheCalcUniverse — Free Online Calculators
> 332+ free, fast, and accurate online calculators for finance, math, health, fitness, DIY, e-commerce, engineering, automotive, developer tools, industrial trades, and everyday life. Zero signup required. Formulas verified against authoritative sources.

## Finance
- [Amortization Calculator](https://thecalcuniverse.com/en/finance/amortization-calculator): Full amortization schedule with extra payment comparison charts
- [APR Calculator](https://thecalcuniverse.com/en/finance/apr-calculator): True APR calculation factoring origination fees, points, and closing costs
- [401(k) Calculator](https://thecalcuniverse.com/en/finance/401k-calculator): Project 401(k) balance with salary growth, employer match, and contribution limits
- [Compound Interest Calculator](https://thecalcuniverse.com/en/finance/compound-interest-calculator): Compound growth with flexible contribution schedules and compounding frequency
- [Investment Calculator](https://thecalcuniverse.com/en/finance/investment-calculator): Project portfolio growth with regular contributions over time
- [Mortgage Calculator](https://thecalcuniverse.com/en/finance/mortgage-calculator): Monthly payment with full amortization breakdown and extra payment options
- [Retirement Calculator](https://thecalcuniverse.com/en/finance/retirement-calculator): How much you need to retire comfortably with inflation adjustment
- [Loan Calculator](https://thecalcuniverse.com/en/finance/loan-calculator): Compare loan options with amortization schedule and total interest cost
- [ROI Calculator](https://thecalcuniverse.com/en/finance/roi-calculator): Return on investment with profit analysis and annualized return
- [Annuity Payout Calculator](https://thecalcuniverse.com/en/finance/annuity-payout-calculator): Lump sum versus annuity depletion projections
- [Credit Card Payoff Calculator](https://thecalcuniverse.com/en/finance/credit-card-payoff-calculator): Debt payoff timeline, interest savings with extra payments
- [Simple Interest Calculator](https://thecalcuniverse.com/en/finance/simple-interest-calculator): Simple interest for loans and investments
- [Rent vs Buy Calculator](https://thecalcuniverse.com/en/finance/rent-vs-buy-calculator): Compare renting versus buying a home with break-even analysis
- [Salary Calculator](https://thecalcuniverse.com/en/finance/salary-calculator): Hourly to salary conversions, take-home pay, and tax estimates
- [All 82 Finance Calculators](https://thecalcuniverse.com/en/finance)

## Health & Fitness
- [BMI Calculator](https://thecalcuniverse.com/en/health/bmi-calculator): Body mass index with BMI categories, charts, and limitations
- [Calorie Calculator](https://thecalcuniverse.com/en/health/calorie-calculator): Daily calorie needs based on age, gender, height, weight, and activity level
- [Body Fat Calculator](https://thecalcuniverse.com/en/health/body-fat-calculator): Body fat percentage estimation using multiple methods
- [BMR Calculator](https://thecalcuniverse.com/en/health/bmr-calculator): Basal metabolic rate using Mifflin-St Jeor equation
- [TDEE Calculator](https://thecalcuniverse.com/en/health/tdee-calculator): Total daily energy expenditure with activity multipliers
- [Macro Calculator](https://thecalcuniverse.com/en/health/macro-calculator): Daily macronutrient targets for weight loss, maintenance, or muscle gain
- [Heart Rate Zone Calculator](https://thecalcuniverse.com/en/health/heart-rate-zone-calculator): Target heart rate zones using Karvonen formula
- [Blood Alcohol Calculator](https://thecalcuniverse.com/en/health/blood-alcohol-calculator): BAC estimation with metabolism time
- [Pregnancy Due Date Calculator](https://thecalcuniverse.com/en/health/pregnancy-due-date-calculator): Estimated due date and pregnancy week-by-week timeline
- [Lean Body Mass Calculator](https://thecalcuniverse.com/en/health/lean-body-mass-calculator): LBM using Boer, James, and Hume formulas
- [All 33 Health Calculators](https://thecalcuniverse.com/en/health)

## Mathematics
- [Percentage Calculator](https://thecalcuniverse.com/en/math/percentage-calculator): All percentage operations with step-by-step solutions
- [Standard Deviation Calculator](https://thecalcuniverse.com/en/math/standard-deviation-calculator): Population and sample standard deviation with variance
- [Scientific Calculator](https://thecalcuniverse.com/en/math/scientific-calculator): Full scientific calculator with trigonometric, logarithmic, and statistical functions
- [Fraction Calculator](https://thecalcuniverse.com/en/math/fraction-calculator): Fraction arithmetic, simplification, and conversion
- [Area & Perimeter Calculator](https://thecalcuniverse.com/en/math/area-perimeter-calculator): Circles, rectangles, triangles, squares, trapezoids, parallelograms, hexagons
- [Pythagorean Theorem Calculator](https://thecalcuniverse.com/en/math/pythagorean-theorem-calculator): Right triangle calculations with hypotenuse and leg solving
- [Mean Median Mode Calculator](https://thecalcuniverse.com/en/math/mean-median-mode-calculator): Measures of central tendency
- [Sig Fig Calculator](https://thecalcuniverse.com/en/math/sig-fig-calculator): Significant figures with rounding rules
- [Correlation Coefficient Calculator](https://thecalcuniverse.com/en/math/correlation-coefficient-calculator): Pearson correlation with scatter plot
- [Angle Converter](https://thecalcuniverse.com/en/math/angle-converter): Degrees, radians, gradians, arcminutes, arcseconds
- [All 88 Math Calculators](https://thecalcuniverse.com/en/math)

## Everyday Life
- [Age Calculator](https://thecalcuniverse.com/en/everyday/age-calculator): Exact age in years, months, days with days until next birthday
- [Time Calculator](https://thecalcuniverse.com/en/everyday/time-calculator): Add, subtract, and convert between time units
- [Date Calculator](https://thecalcuniverse.com/en/everyday/date-calculator): Date difference, addition, and business days
- [Tip Calculator](https://thecalcuniverse.com/en/everyday/tip-calculator): Tip amounts with customizable percentages and split bill
- [Unit Converter](https://thecalcuniverse.com/en/everyday/unit-converter): Multi-unit conversion across length, mass, volume, temperature, and more
- [Sleep Calculator](https://thecalcuniverse.com/en/everyday/sleep-calculator): Optimal bedtime and wake-up time based on sleep cycles
- [All 34 Everyday Calculators](https://thecalcuniverse.com/en/everyday)

## E-Commerce
- [Amazon FBA Calculator](https://thecalcuniverse.com/en/ecommerce/amazon-fba-calculator): Amazon fees, profit, and ROI calculation for sellers
- [Profit Margin Calculator](https://thecalcuniverse.com/en/ecommerce/profit-margin-calculator): Gross margin, markup, and net profit calculations
- [ROAS Calculator](https://thecalcuniverse.com/en/ecommerce/roas-calculator): Return on ad spend with break-even analysis
- [Break-Even Calculator](https://thecalcuniverse.com/en/ecommerce/break-even-calculator): Break-even point in units and revenue
- [AI Token Pricing Calculator](https://thecalcuniverse.com/en/ecommerce/ai-token-pricing): Compare GPT-4o, Claude 3.5 Sonnet, and Gemini pricing with DAU scaling
- [All 13 E-Commerce Calculators](https://thecalcuniverse.com/en/ecommerce)

## Automotive
- [Fuel Cost Calculator](https://thecalcuniverse.com/en/automotive/fuel-cost-calculator): Trip fuel cost for gas and electric vehicles
- [MPG Calculator](https://thecalcuniverse.com/en/automotive/mpg-calculator): Miles per gallon with cost per mile analysis
- [Auto Loan Calculator](https://thecalcuniverse.com/en/automotive/auto-loan-calculator): Car loan payments with amortization schedule
- [Lease vs Buy Calculator](https://thecalcuniverse.com/en/automotive/lease-vs-buy-calculator): Compare leasing versus financing a vehicle
- [Car Depreciation Calculator](https://thecalcuniverse.com/en/automotive/car-depreciation-calculator): Vehicle value projections over time
- [All 13 Automotive Calculators](https://thecalcuniverse.com/en/automotive)

## Home DIY
- [Paint Calculator](https://thecalcuniverse.com/en/diy/paint-calculator): Paint needed for walls, ceilings, and trim
- [Tile Calculator](https://thecalcuniverse.com/en/diy/tile-calculator): Tile quantity with waste factor and cost estimation
- [Concrete Calculator](https://thecalcuniverse.com/en/diy/concrete-calculator): Concrete volume in cubic yards, cubic feet, and cubic meters
- [Renovation Budget Calculator](https://thecalcuniverse.com/en/diy/renovation-budget-calculator): Home remodeling budget with contingency planning
- [Lumber Calculator](https://thecalcuniverse.com/en/diy/lumber-calculator): Board feet calculation and lumber cost estimator
- [All 14 Home DIY Calculators](https://thecalcuniverse.com/en/diy)

## Engineering
- [Ohm's Law Calculator](https://thecalcuniverse.com/en/engineering/ohms-law-calculator): Voltage, current, resistance, and power calculations
- [Voltage Drop Calculator](https://thecalcuniverse.com/en/engineering/voltage-drop-calculator): Wire voltage drop for copper and aluminum conductors
- [Resistor Color Code Calculator](https://thecalcuniverse.com/en/engineering/resistor-color-code-calculator): Decode 3-6 band resistor color codes
- [Wire Size Calculator](https://thecalcuniverse.com/en/engineering/wire-size-calculator): Appropriate wire gauge and conduit fill
- [Pipe Flow Calculator](https://thecalcuniverse.com/en/engineering/pipe-flow-calculator): Flow rate, velocity, and pressure drop
- [All 19 Engineering Calculators](https://thecalcuniverse.com/en/engineering)

## Developer Tools
- [Base64 Encoder/Decoder](https://thecalcuniverse.com/en/devtools/base64-encoder-decoder): Encode and decode base64 strings
- [JSON Formatter & Validator](https://thecalcuniverse.com/en/devtools/json-formatter): JSON validation, formatting, and minification
- [UUID Generator](https://thecalcuniverse.com/en/devtools/uuid-generator): Generate random UUID v4 identifiers
- [Cron Expression Parser](https://thecalcuniverse.com/en/devtools/cron-expression-parser): Human-readable cron schedule explanations
- [Regex Tester](https://thecalcuniverse.com/en/devtools/regex-tester): Regular expression testing with match highlighting
- [All 14 Developer Calculators](https://thecalcuniverse.com/en/devtools)

## Industrial & Trades
- [Torque Calculator](https://thecalcuniverse.com/en/industrial/torque-calculator): Force and lever arm torque calculations with units
- [Pressure Converter](https://thecalcuniverse.com/en/industrial/pressure-converter): Convert between PSI, bar, Pa, kPa, MPa, atm, torr
- [Flow Rate Calculator](https://thecalcuniverse.com/en/industrial/flow-rate-calculator): Volumetric flow rate with pipe diameter and velocity
- [Energy Converter](https://thecalcuniverse.com/en/industrial/energy-converter): Energy unit conversion across all common units
- [All 22 Industrial Calculators](https://thecalcuniverse.com/en/industrial)

## Blog
- [Compound Interest Guide](https://thecalcuniverse.com/en/blog/compound-interest-guide): How compound interest works, the formula, and why starting early matters
- [BMI Guide](https://thecalcuniverse.com/en/blog/bmi-guide-health): Body mass index explained — what it measures and its limitations
- [ROI Guide](https://thecalcuniverse.com/en/blog/what-is-roi-and-how-to-calculate-it): Return on investment formula with real-world examples
- [Amortization Schedules Explained](https://thecalcuniverse.com/en/blog/amortization-schedule-explained): How amortization works for mortgages and loans
- [Retirement Planning](https://thecalcuniverse.com/en/blog/retirement-planning-calculator): How much to save for retirement by age and income level
- [Mortgage Tips Guide](https://thecalcuniverse.com/en/blog/mortgage-calculator-tips): How to use a mortgage calculator for home buying decisions
- [How to Calculate APR](https://thecalcuniverse.com/en/blog/how-to-calculate-apr): APR formula explained with examples for credit cards, mortgages, and personal loans
- [How to Calculate Percentage Change](https://thecalcuniverse.com/en/blog/calculate-percentage-change): Percentage increase and decrease explained with formulas
- [All 65 Blog Posts](https://thecalcuniverse.com/en/blog)

## More
- [All Calculators](https://thecalcuniverse.com/en/calculators): Complete list of all 332+ calculators
- [About](https://thecalcuniverse.com/en/about): About TheCalcUniverse
- [Glossary](https://thecalcuniverse.com/en/glossary): Financial and mathematical terms explained
- [Privacy Policy](https://thecalcuniverse.com/en/privacy): Privacy-first, no data stored
- [Compare Rent vs Buy](https://thecalcuniverse.com/en/compare/finance/rent-vs-buy-analysis): Rent versus buy deep-dive comparison
- [Compare Simple vs Compound Interest](https://thecalcuniverse.com/en/compare/finance/simple-vs-compound-interest): Interest type comparison