Free Online Calculators
Fast, accurate calculators for every need. No signup required — just run the numbers.
⭐ Popular Calculators
🏃 Running
10K Training Pace Calculator
Calculate your ideal training paces for a 10K goal time. Get easy, tempo, interval, and long-run …
5K Training Pace Calculator
Get personalized training paces for your 5K goal time. Calculate easy, tempo, interval, and long-run …
Age Graded Running Calculator – WMA Score
Calculate your age-graded running performance score. Compare your time to world-class athletes of …
Boston Qualifying Time Calculator – BQ by Age
Find your Boston Marathon qualifying time based on age and gender. See the official BAA qualifying …
Easy Run Pace Calculator
Calculate your recovery and easy run pace from a recent race result. Ensure you're training at the …
Elevation Gain Adjustment Calculator – Hill Running Pace Adjuster
Adjust your running pace for elevation gain and hills. Uses Minetti's energy cost equations to …
Half Marathon Pace Calculator – 13.1 Mile Split Planner
Plan your 13.1 mile race with a target finish time. Get per-mile and per-km paces plus every mile …
Heart Rate Drift Calculator
Estimate cardiac drift during long runs. Calculate how much your heart rate rises at the same pace …
Heat Running Pace Adjustment Calculator – Temperature & Humidity Effect
Adjust your expected running pace for heat and humidity. Calculate how much slower to run in hot …
Lactate Threshold Pace Calculator
Calculate your lactate threshold pace from recent race times. Find the exact pace for tempo runs to …
Marathon Pace Calculator – 26.2 Mile Split Planner
Set a 26.2 mile goal time and instantly see your required pace per mile and per km, with key …
Marathon Wall Calculator
Predict when you'll hit the wall in a marathon based on your glycogen stores, pace, and body weight. …
34 calculators💪 Fitness & Health
Adjusted Body Weight Calculator
Calculate Adjusted Body Weight (AdjBW) for obese patients. Used in clinical settings for accurate …
Alcohol Unit Calculator
Calculate alcohol units in your drinks based on volume and ABV. Track weekly intake against health …
Baby Weight Percentile Calculator — WHO Growth Chart Percentile
Baby Weight Percentile Calculator: enter age, gender & weight → instant WHO growth chart percentile. …
Blood Alcohol Calculator - Bac
Estimate Blood Alcohol Concentration (BAC) with the Widmark formula. See DUI legal limits by US …
Blood Alcohol Calculator - Blood Alcohol
Calculate your Blood Alcohol Content (BAC) based on drinks consumed, body weight, and time. Know …
Blood Pressure Calculator
Check your blood pressure reading and understand what your systolic and diastolic numbers mean. Find …
Blood Type Calculator – Predict Child's Blood Type
Free blood type calculator. Enter both parents' blood types (ABO + Rh) to see possible blood types …
BMI Calculator
Free BMI calculator. Check if your weight is underweight, normal, overweight, or obese per WHO …
BMR Calculator
Free BMR calculator using Mifflin-St Jeor and Harris-Benedict equations. Find your Basal Metabolic …
Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy method. Enter your measurements to get an …
Body Surface Area Calculator
Calculate your Body Surface Area (BSA) using the Mosteller, DuBois, or Haycock formula. Used for …
Calorie Deficit Calculator
Calculate the daily calorie deficit needed to reach your goal weight in your target timeframe. Based …
52 calculators💰 Finance
401k Calculator
Estimate your 401(k) retirement savings growth. See how contributions, employer match, and compound …
Amortization Calculator
Calculate your loan amortization schedule, monthly payment, total interest paid, and principal …
Annuity Calculator
Calculate annuity payments, future value, and present value. Supports ordinary annuity and annuity …
Auto Loan Calculator
Calculate monthly car payments, total interest, and total cost of an auto loan. Try this free online …
Bond Yield Calculator
Calculate bond yield to maturity (YTM), current yield, and annual interest income for any bond. This …
Break-Even Calculator
Calculate your break-even point in units and revenue. Find out how many units you need to sell to …
Budget Calculator
Calculate your monthly budget balance. Enter your income and total expenses to see your remaining …
Business Loan Calculator
Calculate monthly business loan payments, total interest, and cost of capital for any commercial …
CAGR Calculator
Calculate Compound Annual Growth Rate (CAGR) between any two values. Find the annualized return of …
Car Lease Calculator
Calculate your monthly car lease payment. Enter vehicle price, residual value, money factor, and …
CD Calculator (Certificate of Deposit)
Calculate the maturity value and interest earned on a Certificate of Deposit (CD). Supports simple …
Child Support Calculator – Estimate Payments
Estimate monthly child support payments using income shares and percentage of income models. …
59 calculators🔢 Math
Absolute Value Calculator
Calculate the absolute value of any number or expression. |x| returns the non-negative magnitude. …
Area Calculator
Calculate the area of common shapes: rectangle, circle, triangle, and trapezoid. This free online …
Average Calculator
Calculate the mean, median, mode, and range of any list of numbers instantly. Enter comma-separated …
Binary Calculator
Perform binary addition, subtraction, multiplication, and division. Convert between binary and …
Circle Calculator
Calculate the area, circumference, and diameter of a circle from the radius. Instant results with …
Cone Volume Calculator
Calculate a cone's volume, slant height, and surface area by entering radius and height. Instant …
Cross Product Calculator
Calculate the cross product of two 3D vectors with step-by-step solution. Use this free online math …
Cylinder Volume Calculator
Calculate the volume and surface area of a cylinder. Enter radius and height to get instant results. …
Distance Formula Calculator
Apply the distance formula √((x₂-x₁)²+(y₂-y₁)²) to find the length between any two points. …
Distance Formula Calculator — Find Distance Between Two Points (Instant)
Use the distance formula to calculate the straight-line distance between two points. Enter x₁, y₁, …
Exponent Calculator
Calculate powers and exponents. Find the result of any base raised to any power. This free online …
Factorial Calculator
Calculate the factorial of any non-negative integer. n! = n × (n-1) × … × 2 × 1. This free online …
58 calculators🔄 Conversions
Acres to Hectares Converter
Convert acres to hectares for land surveys, farms, and real estate listings. Includes area …
Acres to Square Feet Converter — ac to sq ft (Instant, Free)
Convert acres to square feet and square feet to acres instantly. Essential for real estate, land …
Amps to Watts Converter
Convert amps to watts using voltage. Calculate power consumption from current and voltage for any …
Bar to PSI Converter
Convert bar to PSI and PSI to bar instantly. Essential for tire pressure, hydraulics, and gas …
Binary to Decimal Converter
Convert binary numbers to decimal and decimal to binary instantly. Supports up to 64-bit numbers. …
BTU to Watts Converter
Convert BTU/hr to watts and watts to BTU/hr. Used for air conditioning, heating, and appliance …
Bytes to MB Converter — Convert Bytes to Megabytes Instantly
Convert bytes to megabytes (MB) instantly. Uses the binary definition: 1 MB = 1,048,576 bytes. …
Calories to Joules Converter — cal to J (Instant, Free)
Convert food Calories (kcal) and small calories to joules instantly. Includes kJ reference, …
Celsius to Fahrenheit Converter
Convert Celsius to Fahrenheit, Kelvin, and Rankine in one step. Ideal for weather, science, and …
Celsius to Kelvin Converter — °C to K (Instant, Free)
Convert Celsius to Kelvin instantly online. Formula: K = °C + 273.15. Includes conversion table, …
CM to Inches Converter — 175.3 cm = 5'9" | 170 cm = 5'7" | Instant Height Converter
Convert cm to inches instantly: 175.3 cm = 69.02 in (5′9.02″), 170 cm = 5′7″, 180 cm = 5′11″. Type …
CM to MM Converter — cm to mm (Instant, Free)
Convert centimeters to millimeters and millimeters to centimeters instantly. Simple formula: …
99 calculators📅 Date & Time
Add Days to Date Calculator
Add or subtract any number of days to a date. Find the resulting date and day of the week instantly. …
Age Calculator
Calculate your exact age in years, months, days, hours, and minutes. Find out how many days you've …
Age Difference Calculator
Calculate the exact age difference between two people in years, months, and days. This free online …
Birthday Day Calculator
Find out what day of the week you were born on and what day your next birthday falls on. Use this …
Business Days Calculator
Count the number of business days (weekdays) between two dates, excluding weekends. Try this free …
Date Difference Calculator — How Many Days Between Two Dates?
Date Difference Calculator: how many days between two dates? Enter start & end date → instant result …
Days Between Dates Calculator
Calculate the exact number of days between two dates. Find business days, weekdays, weekends, and …
Days Until Calculator
Calculate how many days until a specific date. Countdown to birthdays, holidays, events, and …
Time Add & Subtract Calculator — Add or Subtract Hours, Minutes, Seconds
Add or subtract hours, minutes & seconds from any time instantly. Enter start time + duration → get …
Time Duration Calculator
Find the exact duration between two times in hours, minutes, and seconds. Great for work logs and …
Time Zone Converter
Convert time between time zones. See what time it is anywhere in the world right now. Try this free …
Weeks Calculator
Calculate the number of weeks between two dates or find a date a certain number of weeks from now. …
🏠 Everyday
Aspect Ratio Calculator
Calculate the aspect ratio of any width and height. Resize while maintaining proportions. Supports …
Bra Size Calculator
Find your correct bra size by entering your band and bust measurements. Get your size in US, UK, and …
Cat Age Calculator
Convert your cats age to human years. Cats age faster in their first two years. Use this free online …
Data Transfer Speed Calculator
Calculate how long it will take to transfer a file based on file size and network speed. Use this …
Dog Age Calculator
Convert your dogs age to human years using the latest scientific research. Try this free online tool …
Electricity Bill Calculator
Free electricity bill calculator. Enter your kWh usage and rate to estimate your monthly electricity …
Electricity Cost Calculator — kWh Cost at Any Rate (0.01–0.30 kWh)
Calculate electricity cost instantly. Enter watts + hours/day → monthly & yearly cost at your rate. …
Fuel Cost Calculator
Calculate trip fuel cost based on distance, fuel efficiency, and current gas price. Use this free …
Gas Mileage Calculator
Calculate your fuel efficiency in MPG or L/100km and estimate fuel costs. Try this free online tool …
Grade Calculator
Calculate your weighted average grade from multiple assignments and their weights. This free tool …
Hours Calculator
Calculate total hours worked between start and end times, with break deduction. Use this free online …
Love Calculator
Fun love compatibility calculator! Enter two names and see your love match percentage. Just for …
20 calculators🔬 Science & Engineering
Half-Life Calculator
Free half-life calculator for radioactive decay and drug elimination. Enter initial amount, …
IP Address Calculator – Subnet, CIDR, Network Calculator
Free IP address calculator. Enter an IP and subnet mask to get network address, broadcast, host …
Wire Gauge Calculator
Free wire gauge calculator. Find the correct AWG wire size for any circuit. Enter current (amps), …
🔨 Construction & DIY
Board Foot Calculator
Free board foot calculator. Calculate lumber volume in board feet, estimate material costs, and plan …
Cubic Yard Calculator
Free cubic yard calculator. Convert length, width, and depth measurements into cubic yards, cubic …
Roof Calculator
Free roof calculator. Estimate roof area, number of shingles, squares, and materials needed for any …
Free Online Calculators for Every Need
Welcome to RunCalc — your go-to resource for free, accurate online calculators covering math, finance, health, fitness, running, and much more. No signup required. No ads cluttering your results. Just fast, reliable tools that work instantly in your browser.
What You’ll Find on RunCalc
RunCalc hosts 256+ calculators organized across dozens of categories, from everyday arithmetic to specialized financial planning tools. Whether you’re training for a marathon, budgeting your savings, or doing quick unit conversions, we have a calculator for that.
Top Categories:
- 🏃 Running & Fitness — Pace Calculator, VO2 Max Calculator, Calorie Calculator, Heart Rate Calculator
- 💰 Finance — Compound Interest Calculator, Loan Calculator, Emergency Fund Calculator, Debt Payoff Calculator
- 📐 Math — Percentage Calculator, Fraction Calculator, Square Root Calculator
- 🏥 Health — BMI Calculator, BMR Calculator, Ideal Weight Calculator
- 🔢 Unit Conversions — Miles to KM, KG to LBS, Celsius to Fahrenheit
Why Use RunCalc?
Free, always. Every calculator on this site is 100% free — no premium tiers, no paywalls, no account required. Just open the page and start calculating.
Fast and accurate. Our calculators run entirely in your browser. Results appear instantly as you type, with no server round-trips slowing you down. Formulas are verified against authoritative sources.
Available in 33 languages. RunCalc is fully localized for a global audience. Switch to your preferred language using the language selector at the top of any page.
Mobile-friendly. Every tool is designed to work beautifully on phones, tablets, and desktops alike.
Start Calculating
Browse by category, search for a specific calculator, or jump straight to one of our most popular tools above. If you can’t find what you’re looking for, check our full list of calculators — new tools are added regularly.