Free Calculators and Unit Converters
Whether you need to convert inches to centimeters, calculate a tip, plan your macros, or figure out how much concrete to buy, ConvertNinjas has you covered. Every tool runs instantly in your browser with no signup required.
Instant Results
Every calculator runs right in your browser. No waiting, no page reloads, no server requests.
Privacy First
Your data never leaves your device. We do not store any inputs or results on our servers.
Works Everywhere
Designed for phones, tablets, and desktops so you can convert on the go or at your desk.
Always Free
Every single tool on ConvertNinjas is free to use with no hidden fees or premium tiers.
Browse All Tools
Jump straight into our converters and calculators, organized by category.
Length & Distance
Convert inches, feet, miles, meters, kilometers and more
Weight & Mass
Convert pounds, kilograms, ounces, grams and more
Volume & Cooking
Convert cups, tablespoons, liters, gallons and cooking measures
Area
Convert square feet, square meters, acres and hectares
Temperature
Convert Fahrenheit, Celsius and Kelvin
Speed & Pace
Convert mph, km/h, knots, and running pace
Data & Media
Convert bytes, bandwidth, DPI and aspect ratios
Time & World
Time zone converter, meeting planner and DST checker
Currency & Fees
Currency converter, tip calculator, tax and discount tools
Energy & Power
Convert kWh, joules, watts, kilowatts, calories and kilojoules
Pressure
Convert PSI, bar, kPa and atmospheres
Clothing & Shoe Sizes
Convert US, UK, EU shoe and clothing sizes
Angles
Convert between degrees and radians
Fitness & Nutrition
TDEE, BMR, macros, 1RM, running pace and calorie tools
Student Calculators
GPA, grade calculators, study planner and reading time
Home & Setup Fit
TV sizing, rug fit, paint estimator and furniture tools
Fun & Food
Pizza size calculators for adults and kids
Cooking & Baking
Recipe scaler, oven temperatures, and baking conversions
Finance & Investing
Loan EMI, mortgage, compound interest and salary calculators
Gas & Fuel
MPG, L/100km, km/L conversions and trip fuel cost estimator
Construction & DIY
Concrete, mulch, lumber and tile estimators for projects
Electrical
Volts, amps, watts calculator, kW to HP, and cord sizing
Weather
Wind chill, heat index and dew point calculators
Automotive
Tire size comparison, speedometer error, and torque conversion
Cryptocurrency
Live crypto to USD converter for top 10 cryptocurrencies
Language & Text
Word count, character counter, reading time and case converter
Translation
Translate English text to Spanish, Hindi and more
Document Tools
Convert Word documents to PDF and more
Science & Chemistry
Molar mass, concentration and pH calculators for students
Sports Equipment Sizing
Find the right equipment size for any age group
Math
Solve proportions, ratios and everyday math problems
How ConvertNinjas Works
Three simple steps to get the answer you need.
Pick a Tool
Browse our categories or search for the converter or calculator you need. We cover units, finance, fitness, cooking, home improvement, and much more.
Enter Your Values
Type in the number you want to convert or fill in the fields for your calculation. Results appear instantly as you type, so there is nothing extra to click.
Use Your Results
Copy the result, take a screenshot, or just remember it. Every tool includes educational context so you understand the math behind the answer.
Why Unit Conversions Matter in Everyday Life
Unit conversions are part of daily life whether you realize it or not. Cooking a recipe from a British food blog means converting grams to cups. Shopping for furniture online from a European retailer means converting centimeters to inches. Planning a road trip in Canada means converting kilometers to miles. Even something as simple as checking the weather forecast while traveling abroad requires a quick Fahrenheit to Celsius conversion. Having a reliable, fast converter at your fingertips saves time and prevents costly mistakes.
Built for Students, Professionals, and Everyone in Between
ConvertNinjas started because we kept running into the same problem: scattered, ad-heavy converter sites that gave you a number with no context. We wanted tools that not only give you the right answer but also explain the reasoning. That is why every tool page includes quick facts, conversion formulas, and real-world examples. Students can use our GPA converter and grade calculators to plan their academic goals. Fitness enthusiasts can calculate their TDEE, macros, and one-rep max in one place. Home improvers can estimate paint, tile, and concrete quantities before heading to the hardware store. And travelers can convert currencies, plan across time zones, and compare cash vs card fees for their next trip.
Accuracy You Can Trust
Every conversion factor on ConvertNinjas comes from internationally recognized standards. Our length conversions use the exact 1 inch = 25.4 millimeters definition adopted by the International Yard and Pound Agreement of 1959. Temperature conversions use the precise formulas linking Fahrenheit, Celsius, and Kelvin. Financial calculators use standard amortization and compound interest formulas used by banks and lenders worldwide. We also include notes about edge cases, like the difference between US and UK fluid ounces or the distinction between short tons and metric tonnes, so you always know exactly what you are calculating.