Free Online Calculators & Converters
Fast, single-page tools for everyday math, health, finance, and more. Pick one, get your answer. No sign-up, and nothing you enter ever leaves your browser.
Finance
- Mortgage CalculatorEstimate your monthly mortgage payment.
- Percentage CalculatorCalculate percentages and percentage change.
- Tip CalculatorSplit a bill and calculate the tip instantly.
- Loan CalculatorEstimate loan payments, total interest, and payoff date.
- Auto Loan CalculatorEstimate monthly car payments, including trade-in and sales tax.
- Discount CalculatorCalculate a sale price, savings, and stacked discounts.
- Compound Interest CalculatorSee how savings grow over time with compound interest.
- Simple Interest CalculatorCalculate interest and total amount with simple (non-compounding) interest.
- Salary CalculatorConvert pay between hourly, weekly, monthly, and annual.
- Interest Rate CalculatorFind the interest rate from a loan amount, payment, and term.
- ROI CalculatorCalculate return on investment and annualized ROI.
Everyday & Planning
- Age CalculatorFind your exact age in years, months, and days.
- Date CalculatorFind days between dates, or add/subtract days.
- Time CalculatorFind the duration between two times, or add/subtract time.
- Cooking Measurement ConverterConvert cooking measurements by ingredient.
- Shoe Size ConverterConvert shoe sizes between US, UK, EU, and cm.
- Time Zone Meeting PlannerFind the best time to meet across time zones.
- Gas Mileage CalculatorCalculate fuel economy in MPG, km/L, and L/100km.
- Fuel Cost CalculatorEstimate trip fuel cost from distance, fuel economy, and price.
- Wind Chill CalculatorCalculate how cold it feels from temperature and wind speed.
- Heat Index CalculatorCalculate how hot it feels from temperature and humidity.
Health & Fitness
- BMI CalculatorCalculate your BMI and weight category.
- Calorie CalculatorEstimate your daily calorie needs.
- Pregnancy CalculatorEstimate your due date, trimester, and milestones.
- Ovulation CalculatorPredict your fertile window and next period from your cycle.
- Body Fat CalculatorEstimate body fat percentage from tape measurements.
- Ideal Weight CalculatorEstimate your ideal body weight from height and gender.
- Sleep CalculatorFind the best bedtime or wake up time based on sleep cycles.
- Target Heart Rate CalculatorFind your target heart rate zones for exercise by age.
- One Rep Max CalculatorEstimate your one rep max from a weight and rep count.
- Calories Burned CalculatorEstimate calories burned by activity, weight, and duration.
- Macro CalculatorSplit a calorie target into protein, carb, and fat grams.
- Pace CalculatorConvert between running pace, time, and distance.
Math
- Unit ConverterConvert length, weight, and temperature units.
- Basic CalculatorA simple calculator for everyday math.
- Scientific CalculatorTrigonometry, logarithms, powers, roots, and more.
- GPA CalculatorCalculate your cumulative GPA from your courses.
- Grade CalculatorCalculate your overall grade from weighted categories.
- Fraction CalculatorAdd, subtract, multiply, or divide fractions.
- Random Number GeneratorGenerate random numbers within any range.
- Right Triangle CalculatorSolve a right triangle's sides and angles, including the Pythagorean theorem.
- Area CalculatorFind the area and perimeter of circles, squares, rectangles, triangles, and trapezoids.
- Volume CalculatorFind the volume and surface area of cubes, boxes, spheres, cylinders, and cones.
- Statistics CalculatorMean, median, mode, range, and standard deviation from a dataset.
- Permutation and Combination CalculatorCalculate permutations (nPr) and combinations (nCr) from n and r.
- Percent Error CalculatorCalculate percent error between an experimental and theoretical value.
- Quadratic Formula CalculatorSolve ax² + bx + c = 0 for x, including complex roots.
- Ohm's Law CalculatorSolve for voltage, current, resistance, or power.
- GCF and LCM CalculatorFind the greatest common factor and least common multiple of a list of numbers.
Text & Developer Tools
- Word CounterCount words, characters, sentences, and paragraphs.
- Password GeneratorGenerate strong, random passwords instantly.
- Case ConverterConvert text to UPPERCASE, camelCase, snake_case, and more.
- Base64 & URL Encoder/DecoderEncode or decode text as Base64, or encode/decode URL components.
- Number Base ConverterConvert between binary, octal, decimal, and hexadecimal.
- IP Subnet CalculatorCalculate subnet mask, network, and host range from CIDR notation.
- Roman Numeral ConverterConvert between numbers and Roman numerals.
Guides
Want the reasoning behind the numbers, not just the answer? These go deeper than any single calculator, on the topics people ask about most.
- How Mortgage Amortization Actually Works
- How Compound Interest Actually Works
- BMI Explained: What It Measures, and Where It Falls Short
- GPA Explained: Weighted vs. Unweighted, and How Credit Hours Work
- A Practical Guide to Kitchen Measurement Conversions
- Body Fat Percentage Explained: The Navy Method and Its Limits
- Target Heart Rate Zones Explained: The Karvonen Method
- Mean, Median, and Standard Deviation Explained
- How the Quadratic Formula Actually Works
- How Due Dates and Ovulation Are Actually Calculated