Currency Converter
Convert between 30+ world currencies with live daily exchange rates. Free, instant results.
Finance
Mortgage Calculator
Calculate monthly payments, total interest, and amortization schedule for your home loan.
Finance
Loan Calculator
Estimate monthly payments and total cost for personal loans, auto loans, and more.
Finance
Compound Interest
See how your savings grow over time with compound interest and regular contributions.
Finance
Savings Calculator
Calculate how long to reach your savings goal or how much to save monthly.
Finance
Inflation Calculator
See how inflation affects purchasing power over time.
Finance
Salary Calculator
Convert between hourly, daily, weekly, biweekly, monthly, and annual salary.
Finance
Paycheck Calculator
Calculate take-home pay after taxes, FICA, and deductions.
Finance
Tip Calculator
Calculate tip amount and split the bill between multiple people.
Finance
Investment Return
Calculate ROI, annualized returns, and compare investment performance.
Finance
Tax Estimator
Estimate your federal income tax, effective rate, and see a bracket-by-bracket breakdown.
Finance
Retirement Calculator
Plan your retirement savings with 401(k) match, compound growth, and the 4% rule.
Finance
Rent vs Buy
Should you rent or buy? Compare total costs including equity, appreciation, and opportunity cost.
Finance
Car Lease vs Buy
Compare the total cost of leasing versus buying a car over your ownership period.
Finance
Auto Loan Calculator
Calculate monthly car payments, total interest, and true cost.
Finance
Net Worth
Track your personal balance sheet - assets minus liabilities with age benchmarks.
Finance
Fuel Cost Calculator
Estimate fuel costs for any trip based on distance, MPG, and gas price.
Finance
Debt Payoff Calculator
See when you'll be debt-free and how much extra payments save in interest.
Finance
FIRE Calculator
Calculate your financial independence number and how many years until you can retire early.
Finance
Mortgage Refinance
Compare your current mortgage to a new offer - see monthly savings and break-even month.
Finance
Percentage Calculator
Calculate percentages, percentage change, what percent one number is of another.
Math
Average Calculator
Calculate mean, median, mode, geometric mean, harmonic mean, and weighted average for any list of numbers.
Math
Fraction Calculator
Add, subtract, multiply, and divide fractions with step-by-step solutions.
Math
Standard Deviation Calculator
Calculate population and sample standard deviation, variance, mean, median, mode, and more.
Math
Random Number Generator
Generate random integers or decimals, single or multiple values, with optional duplicate prevention and sorting.
Math
Unit Converter
Convert between units of length, weight, temperature, volume, area, and more.
Math
Scientific Calculator
Full scientific calculator with trig, logarithms, exponents, and memory functions.
Math
Programmer Calculator
Convert hex, decimal, binary, octal. Apply bitwise AND/OR/XOR/NOT/shift at 8/16/32/64-bit width.
MathDev
Graphing Calculator
Plot functions, parametrics, and polar curves. Pan, zoom, save as PNG.
Math
Square Root Calculator
Square roots, cube roots, Nth roots, radical simplification, perfect square check, and prime factorization.
Math
Exponent Calculator
Raise any base to any power, view common powers, and calculate logarithms.
Math
Ratio Calculator
Simplify ratios, solve proportions, scale values, and calculate aspect ratios.
Math
Probability Calculator
Calculate event probability, combinations, permutations, and conditional probability.
Math
Macro Calculator
Calculate TDEE and daily protein, carb, and fat targets using Mifflin-St Jeor. Choose your goal and macro split.
Health
BMI Calculator
Calculate your Body Mass Index and see which category you fall into.
Health
Calorie Calculator
Estimate daily calorie needs based on age, weight, height, and activity level.
Health
Ideal Weight Calculator
Find your ideal weight using 5 medical formulas.
Health
Body Fat Calculator
Estimate body fat % using the US Navy and BMI methods.
Health
Pregnancy Due Date Calculator
Calculate your due date from LMP, IVF transfer, or conception. See gestational age, trimester, and key milestones.
Health
Sleep Cycle Calculator
Find the best time to go to bed or wake up based on 90-minute sleep cycles. Minimize morning grogginess.
Health
Dog Food Calculator
Plan your dog's daily calories, portion sizes, and treat budget based on weight goals.
Health
Water Intake Calculator
Calculate your daily water intake based on weight, exercise, climate, altitude, and pregnancy status.
Health
Age Calculator
Calculate your exact age in years, months, days, hours, and minutes.
Date & Time
Date Difference
Find the number of days, weeks, or months between two dates.
Date & Time
Time Zone Converter
Convert times between any two time zones instantly. See UTC offsets, DST status, and time differences.
Date & Time
Countdown Calculator
Live ticking countdown to any date or event with years, months, days, hours, minutes, and seconds.
Date & Time
Time Calculator
Add or subtract hours, minutes, and seconds. Calculate the difference between two times with cross-midnight support.
Date & Time
Profit Margin
Calculate gross margin, net margin, and markup from cost and revenue.
Business
GPA Calculator
Calculate your semester and cumulative GPA on a 4.0 scale.
Business
Utilization Rate
Calculate billable utilization rate, revenue efficiency, and profit margin for consulting teams.
Business
Break-Even Analysis
Find your break-even point in units and revenue with contribution margin analysis.
Business
Invoice Calculator
Calculate invoice totals with line items, tax, and discounts for freelancers.
Business
Meeting Cost
Calculate the real dollar cost of meetings based on attendee salaries and duration.
Business
Hours Calculator
Calculate hours worked, overtime, and pay from clock in/out times.
Business
RAID Rebuild Risk
Visualize URE probability and data loss risk during RAID array rebuild.
Business
SaaS Metrics Lab
Calculate LTV:CAC ratio, payback period, NRR, and model cohort revenue for SaaS businesses.
Business
Seller Net Sheet
Estimate net proceeds from selling your home after commissions, closing costs, and payoff.
Finance
Moving Budget
Estimate total moving costs including movers, truck rental, packing, and hidden expenses.
Finance
Down Payment Calculator
Calculate your home down payment, loan size, PMI estimate, closing costs, and months to save.
Finance
CD Calculator
Calculate your CD maturity value, total interest earned, APR vs APY, and early withdrawal penalty.
Finance
APR Calculator
Calculate the true APR on any loan including fees, points, and closing costs to see real borrowing cost.
Finance
Debt-to-Income Ratio
Calculate your front-end and back-end DTI plus FHA, conventional, VA, and USDA mortgage qualification.
Finance
Recipe Scaler
Scale any recipe up or down - enter ingredients and adjust servings instantly.
Home & DIY
Electricity Bill Estimator
Estimate your monthly electric bill based on kWh usage and local rates.
Home & DIY
Paint Calculator
Calculate how much paint you need for any room, accounting for doors, windows, and coats.
Home & DIY
Flooring Calculator
Calculate square footage, material, and cost for hardwood, laminate, tile, or carpet.
Home & DIY
Concrete Calculator
Calculate cubic yards, bags, and cost for slabs, footings, and columns.
Home & DIY
HVAC BTU Calculator
Calculate the BTU capacity needed for heating or cooling any room.
Home & DIY
Deck Board Calculator
Calculate boards, screws, joists, and cost for your deck project.
Home & DIY
Energy Cost
Calculate how much any appliance costs to run per day, month, and year.
Home & DIY
Garden Planner
Calculate soil, mulch, and plant spacing for raised beds and garden plots.
Home & DIY
Potting Soil Calculator
Calculate how much potting soil you need for round, rectangular, tapered, and hemisphere pots. Includes bag count.
Home & DIY
Sourdough Calculator
Plan your sourdough bake with fermentation timing, levain builds, and a reverse-scheduling timeline.
Home & DIY
EV Charging Planner
Plan EV road trips with charging curve optimization, stop timing, and temperature-adjusted range.
Home & DIY
Home Battery Runtime
Calculate backup power duration with solar refill cycles during outages.
Home & DIY
Heat Pump Payback
Compare heat pump vs gas costs by climate zone with COP curves and IRA rebates.
Home & DIY
Pool Chemistry
Balance pool water chemistry with Langelier Saturation Index and chemical dosing.
Home & DIY
Homebrew Calculator
Calculate yeast pitch rates, priming sugar, and fermentation pressure for homebrewing.
Home & DIY
Welding Calculator
Calculate carbon equivalent, preheat temperature, and heat input for structural welding.
Home & DIY
3D Printing Calculator
Estimate filament usage, material cost, print time, and electricity for your 3D prints.
Home & DIY
Ham Radio Link Budget
Calculate signal propagation, link margin, and line-of-sight distance for amateur radio.
Home & DIY
Rainwater Harvesting
Size your rainwater tank based on roof area, rainfall patterns, and daily usage needs.
Home & DIY
Solar Panel Savings
Calculate solar panel savings, payback period, ROI, federal tax credit, and CO2 offset.
Home & DIY
Wallpaper Calculator
Calculate exactly how many wallpaper rolls you need, accounting for doors, windows, and pattern repeat.
Home & DIY
Fence Calculator
Calculate fence posts, rails, pickets, concrete bags, and total cost for a complete materials estimate.
Home & DIY
Gravel & Mulch Calculator
Calculate cubic yards, tons, bags, and cost for gravel, mulch, topsoil, sand, and more.
Home & DIY
Tile Calculator
Calculate tiles needed, boxes, grout, thinset mortar, and total cost with waste factor support.
Home & DIY
Hohmann Transfer Orbit
Calculate the delta-v for fuel-efficient two-burn orbital transfers between circular orbits.
Space & Physics
Bi-Elliptic Transfer
Compare 3-burn bi-elliptic vs Hohmann transfers for extreme orbit changes.
Space & Physics
Relativistic Journey
Calculate crew time vs Earth time for constant-acceleration relativistic space travel.
Space & Physics
Relativistic Fuel Ratio
Calculate the exponential antimatter fuel requirements for near-light-speed travel.
Space & Physics
Relativistic Doppler Shift
Visualize blueshift and redshift of light from relativistic-speed sources.
Space & Physics
O'Neill Cylinder Gravity
Find the spin rate needed to simulate Earth gravity inside a cylindrical space habitat.
Space & Physics
Radiation Shielding
Calculate material thickness to shield astronauts using Beer-Lambert attenuation.
Space & Physics
Astrophotography Planner
Calculate max exposure time, field of view, and pixel scale for deep sky imaging.
Space & Physics
Asteroid Impact Effects
Simulate blast, thermal, seismic, and tsunami effects of an asteroid impact at your distance.
Space & Physics
Ice Load Bearing
Calculate maximum safe vehicle weight on frozen lakes using Gold's Formula.
Survival
WBGT Heat Stress
Calculate true military-grade heat stress index accounting for sun and wind.
Survival
Loaded March Calories
Predict metabolic energy cost of hiking with a heavy pack using the Pandolf equation.
Survival
Dead Reckoning
Determine ocean current set and drift by comparing DR position to actual GPS fix.
Survival
Wildfire Defense
Assess ember exposure risk and defensible space zones for your property.
Survival
Scuba Gas Planner
Plan dive gas, rock bottom, turn pressure, and Nitrox MOD for safe diving.
Survival
Aircraft Weight & Balance
Plot CG on the weight/balance envelope for Cessna, Piper, and custom aircraft.
Survival
Time of Death (Henssge)
Estimate post-mortem interval using Henssge's double-exponential body cooling model.
Forensics & History
Blood Alcohol (Watson)
Calculate BAC accurately using Watson's Total Body Water adaptation of Widmark.
Forensics & History
D&D Advantage Probability
Calculate exact hit probability with Advantage, Disadvantage, and modifiers in D&D 5e.
Gaming & Strategy
Hex Grid Distance
Measure distance on hexagonal grids using 3D cube coordinate conversion.
Gaming & Strategy
Elo Rating Probability
Calculate win probability from Elo rating differentials for chess and esports.
Gaming & Strategy
Lindy Effect Lifespan
Predict how long technologies and ideas will survive based on current age.
Gaming & Strategy
Network Value (Metcalfe)
Compare N-squared vs exponential value scaling for communication vs social networks.
Gaming & Strategy
Zipf's Law City Size
Predict any city's population from its rank using Zipf's power law distribution.
Gaming & Strategy
Dunbar's Number
Calculate the cognitive limit of stable social relationships from neocortex ratio.
Gaming & Strategy
Kelly Criterion
Find the mathematically optimal bet size to maximize long-term portfolio growth.
Gaming & Strategy
Sous Vide Pasteurization
Calculate exact pasteurization time for sous vide cooking at any temperature.
Food Science
Spherification Ratios
Calculate sodium alginate and calcium lactate ratios for molecular gastronomy.
Food Science
Coffee Extraction Yield
Hit the SCAA Golden Cup standard by calculating extraction yield from TDS readings.
Food Science
Maillard Reaction Energy
Extract Maillard browning activation energy from two-temperature reaction rate data.
Food Science
Grade Needed Calculator
Find the minimum score you need on a final exam or assignment to reach your target grade.
Education
Pet Age Calculator
Convert your pet's age to human years using modern veterinary formulas by breed size.
Education
One Rep Max (1RM)
Calculate your one rep max using 4 proven formulas with training percentage table and RPE reference.
Fitness & Sports
Pace Calculator
Calculate running pace, finish time, or distance with per-mile splits and race predictions.
Fitness & Sports
VO2 Max Calculator
Estimate your VO2 Max from Cooper run, Rockport walk, or step test with ACSM fitness classification.
Fitness & Sports
Heart Rate Zones
Calculate your 5 heart rate training zones using standard, Tanaka, or Karvonen formulas.
Fitness & Sports
Ohm's Law Calculator
Calculate voltage, current, resistance, and power instantly. Enter any 2 values to get the other 2.
Electrical
LED Resistor Calculator
Calculate the correct resistor for any LED circuit with E24 standard value and color code.
Electrical
Wire Gauge Calculator
Find the correct AWG wire gauge with voltage drop, power loss, and NEC ampacity ratings.
Electrical
Battery Life Calculator
Calculate battery runtime from capacity and current draw. Supports duty cycle and battery comparisons.
Electrical