Free Online Calculators & Unit Converters
Fast, beautiful, and privacy-first. No sign-up required. All calculations run in your browser.
Popular Tools
View All →Financial Calculators
Calculate loans, mortgages, interest, margins, and more.
Loan Calculator
Calculate monthly loan payments, total interest, and amortization.
Mortgage Calculator
Calculate mortgage payments and view amortization schedule.
Compound Interest Calculator
Calculate compound interest and final amount over time.
Margin Calculator
Calculate profit margin, markup, and gross margin.
Discount Calculator
Calculate sale price and discount percentage.
Tip Calculator
Calculate tip amount and split the bill.
Salary Calculator
Convert between annual, monthly, and hourly salary.
Investment ROI Calculator
Calculate Return on Investment for any investment.
Auto Loan Calculator
Calculate car payments including tax and fees.
Savings Calculator
Calculate how your savings grow with compound interest.
GST/VAT Calculator
Add or remove GST/VAT from any amount.
Inflation Calculator
Calculate how inflation affects purchasing power over time.
Unit Converters
Convert between length, weight, temperature, and more.
Length Converter
Convert inches, cm, feet, meters, and more.
Weight Converter
Convert lbs, kg, ounces, grams, and more.
Temperature Converter
Convert Celsius, Fahrenheit, and Kelvin.
Volume Converter
Convert gallons, liters, ml, and more.
Speed Converter
Convert mph, km/h, m/s, and more.
Data Storage Converter
Convert KB, MB, GB, TB, and more.
Area Converter
Convert square feet, acres, hectares, and more.
Pressure Converter
Convert psi, bar, atm, kPa, and more.
Energy Converter
Convert joules, calories, BTU, kWh, and more.
Fuel Economy Converter
Convert MPG, km/L, L/100km.
Date & Time Calculators
Calculate age, date differences, and work days.
Age Calculator
Calculate your exact age in years, months, and days.
Date Difference Calculator
Calculate the number of days between two dates.
Work Days Calculator
Calculate business days between two dates.
Time Calculator
Add or subtract time in hours, minutes, and seconds.
Hours Calculator
Calculate work hours with break deductions.
Math & Everyday Calculators
Percentages, fractions, BMI, calories, and more.
Percentage Calculator
Calculate percentages in multiple ways.
Fraction Calculator
Add, subtract, multiply, and divide fractions.
GCD & LCM Calculator
Calculate Greatest Common Divisor and Least Common Multiple.
Ratio Calculator
Simplify ratios and find equivalent ratios.
Scientific Calculator
Advanced calculator with trig, log, and factorial functions.
Standard Deviation Calculator
Calculate mean, median, mode, variance, and standard deviation.
Grade Calculator
Calculate weighted average and GPA on a 4.0 scale.
BMI Calculator
Calculate your Body Mass Index and weight category.
Calorie Calculator
Calculate your daily calorie needs (TDEE).
Body Fat Calculator
Calculate body fat percentage using the US Navy method.
Pace Calculator
Calculate running pace, speed, and finish time.
Pregnancy Due Date Calculator
Calculate estimated due date and track milestones.
Everyday Tools
Password generators, color converters, random numbers, and more.
Password Generator
Generate strong, secure random passwords.
Random Number Generator
Generate random numbers in any range.
Color Converter
Convert colors between HEX, RGB, HSL.
Number Base Converter
Convert binary, octal, decimal, hex.
Word Counter
Count words, characters, sentences, paragraphs.
Gas Mileage Calculator
Calculate fuel efficiency (MPG or L/100km) and trip fuel costs.
Why CalcKit?
Transparent Formulas
Every calculator shows the exact formula, a step-by-step breakdown, and a worked example — so the math behind each result is never a black box.
45+ Calculators, One Roof
Mortgages, ROI, BMI, calories, fractions, unit conversions — finance, health, math, and everyday utilities sit side by side, no app-hopping required.
Bilingual by Default
Full English and Chinese coverage across every calculator, with consistent terminology and parallel result pages — useful for cross-language classrooms and international teams.