Calculators
Browse 115 free calculators for construction, dates and time, electrical work, fitness, grades, math, geometry and more. Each shows its formula and a worked example.
🏗️ Construction and Home
Square footage, concrete, gravel, stairs, fencing, drywall, roofing and pool volume.
- Square Footage CalculatorCalculate square footage for rectangles, circles, triangles and trapezoids. Results in square feet, square yards, square meters and acres.
- Concrete CalculatorCalculate concrete volume in cubic yards, cubic feet and cubic meters for slabs, footings and round columns, plus the number of 40, 60 and 80 lb bags.
- Concrete Block CalculatorWork out how many concrete blocks a wall needs from its length and height, with openings and a waste allowance.
- Gravel and Stone CalculatorCalculate how much gravel, crushed stone, pea gravel or river rock you need in cubic yards and tons from the area and depth.
- Sand CalculatorEstimate how much sand you need in cubic yards and tons for a sandbox, paver bed, play area or fill, based on area and depth.
- Topsoil and Soil CalculatorCalculate cubic yards and tons of topsoil, fill dirt, compost or mulch for lawns, raised beds and gardens from the area and depth.
- Asphalt CalculatorCalculate tons of hot mix asphalt for a driveway or parking area from length, width and thickness, with adjustable density.
- Stair CalculatorCalculate the number of steps, exact riser height, total run, stringer length and stair angle from the total rise.
- Fence CalculatorEstimate fence posts, sections, rails and pickets from the fence length, post spacing and picket size.
- Drywall CalculatorCalculate how many sheets of drywall or sheetrock a room needs from its dimensions, with doors, windows, ceiling and waste.
- Plywood CalculatorFind how many sheets of plywood or OSB cover a floor, wall or roof deck, based on the area, sheet size and waste allowance.
- Flooring and Carpet CalculatorCalculate flooring or carpet for a room in square feet and square yards, with waste and the number of boxes to buy.
- Roofing Shingle CalculatorCalculate roof area, roofing squares and bundles of shingles from the building footprint and roof pitch.
- Rafter Length CalculatorCalculate common rafter length, roof rise and angle from the building span, roof pitch, ridge thickness and overhang.
- Linear Feet CalculatorConvert square feet to linear feet for boards of any width, convert linear feet back to square feet, or total the linear feet of several pieces.
- Pool Volume CalculatorCalculate how many gallons or liters of water a rectangular, round or oval pool holds from its dimensions and depths.
- Pool Salt CalculatorCalculate how many pounds and bags of salt to add to a saltwater pool to reach a target salinity in ppm.
- Tank Volume CalculatorCalculate the capacity of a rectangular or cylindrical tank or aquarium in gallons and liters, with the weight of the water.
- Pipe Volume CalculatorCalculate the volume of water inside a pipe from its inner diameter and length, in gallons, liters and cubic feet.
- Metal Weight CalculatorCalculate the weight of steel, aluminum, copper and other metals as plate, round bar, square bar or tube from the dimensions.
📅 Date and Time
Days between dates, business days, age, time cards, military time and Unix timestamps.
- Days Between Dates CalculatorCount the days between two dates. See the difference in days, weeks, months and years, plus hours, minutes and weekdays.
- Business Days CalculatorCount the working days between two dates, excluding weekends and optionally US federal holidays or your own list of holidays.
- Date Calculator: Add or Subtract DaysAdd or subtract days, weeks, months, years or business days from a date. Find the date 30, 60, 90 or 180 days from today.
- Age CalculatorCalculate exact age in years, months and days from a date of birth. Also shows total months, weeks, days and the next birthday.
- Day of the Year CalculatorFind the day number of any date, the days left in the year, the ISO week number, the quarter and whether it is a leap year.
- Time Calculator: Add and Subtract TimeAdd and subtract hours, minutes and seconds. Get the total as a duration, in decimal hours, and in minutes and seconds.
- Time to Decimal CalculatorConvert hours and minutes to decimal hours for payroll and timesheets, or convert decimal hours back to hours, minutes and seconds.
- Time Card CalculatorAdd up hours worked from clock-in and clock-out times with unpaid breaks. Shows daily and weekly totals in hours and decimal hours, with overtime.
- Military Time ConverterConvert between military time (24-hour clock) and standard 12-hour AM/PM time. Includes a full military time chart.
- Unix Timestamp ConverterConvert a Unix epoch timestamp to a readable UTC date and time, or convert a date and time to a Unix timestamp in seconds and milliseconds.
- Time Duration CalculatorCalculate the time between two dates and times in days, hours and minutes. Find how many hours passed between two clock times.
⚡ Electrical
Ohm's law, resistor color codes, voltage drop, watts to amps and battery life.
- Ohm's Law CalculatorEnter any two of voltage, current, resistance and power to calculate the other two with Ohm's law and the power formula.
- Resistor Color Code CalculatorDecode 4, 5 and 6 band resistor color codes. Pick the band colors to get the resistance, tolerance range and temperature coefficient.
- Parallel and Series Resistor CalculatorCalculate the equivalent resistance of any number of resistors in parallel or in series. Accepts values such as 470, 4.7k and 1M.
- LED Resistor CalculatorCalculate the series resistor for one or more LEDs from the supply voltage, LED forward voltage and current. Shows the nearest standard value and power rating.
- Watts to Amps CalculatorConvert watts or kilowatts to amps, or amps to watts, for DC, single-phase AC and three-phase AC circuits with power factor.
- Battery Life CalculatorEstimate how long a battery lasts from its capacity in mAh or Ah and the load current, with a usable-capacity factor and watt-hours.
- Voltage Drop CalculatorCalculate voltage drop and percentage drop for copper or aluminum wire by AWG size, length, current and conductor temperature.
- Power Factor CalculatorCalculate power factor, reactive power and phase angle from real power in kW and apparent power in kVA.
- RC Low Pass Filter CalculatorCalculate the cutoff frequency and time constant of an RC low pass or high pass filter from its resistance and capacitance.
- PCB Trace Width CalculatorCalculate the minimum PCB trace width for a given current, temperature rise and copper weight using the IPC-2221 formula.
🏃 Fitness and Running
One rep max, pace, heart rate zones, VO2 max, FFMI and powerlifting scores.
- One Rep Max CalculatorEstimate your one rep max for bench press, squat or deadlift from a weight and reps, using the Epley, Brzycki and other formulas, with a percentage chart.
- FFMI CalculatorCalculate your fat-free mass index (FFMI) and height-normalized FFMI from weight, height and body fat percentage.
- Wilks and DOTS CalculatorCalculate Wilks and DOTS scores for powerlifting from your body weight and total, to compare strength across weight classes.
- VO2 Max CalculatorEstimate VO2 max from the Cooper 12-minute run, a 1.5 mile run time, or your resting and maximum heart rate.
- Heart Rate Zone CalculatorCalculate your maximum heart rate and five training zones from your age, with optional Karvonen zones using resting heart rate.
- Pace CalculatorCalculate running pace per mile and per kilometer from distance and time, or finish time from pace. Includes speed and race time predictions.
- Steps to Miles CalculatorConvert steps to miles and kilometers using your height or stride length. Also shows how many steps are in a mile for you.
🎓 Grades and GPA
Weighted grades, final exam targets, GPA and test scores.
- Grade CalculatorCalculate your weighted course grade from assignment scores and their weights. Shows the percentage, letter grade and remaining weight.
- Final Grade CalculatorFind the score you need on your final exam to reach a target course grade, from your current grade and the weight of the final.
- GPA CalculatorCalculate high school or college GPA on the 4.0 scale from letter grades and credits. Supports weighted honors and AP classes and cumulative GPA.
- Test Score CalculatorTurn the number of questions and wrong answers into a percentage and letter grade. Includes an easy grader chart for the whole test.
🔤 Text, Code and Network
Morse code, binary, hex, Base64, ciphers, subnet masks and file permissions.
- Morse Code TranslatorTranslate text to Morse code and Morse code back to text. Supports letters, numbers and punctuation in International Morse Code.
- Binary Translator: Text to BinaryConvert text to binary code and binary back to text. Uses 8-bit bytes with UTF-8, so it handles ASCII and every other character.
- Hex Translator: Text to HexadecimalConvert text to hexadecimal bytes and hex back to text using UTF-8. Useful for reading hex dumps and encoding strings.
- Base64 Encoder and DecoderEncode text to Base64 or decode Base64 back to text, with full UTF-8 support and a URL-safe variant.
- Text to ASCII and Unicode ConverterConvert text to ASCII codes and Unicode code points in decimal and hex, or turn a list of character codes back into text.
- Caesar Cipher Encoder and SolverEncrypt or decrypt text with a Caesar shift cipher. Shows all 25 possible shifts so you can solve a cipher without knowing the key, including ROT13.
- Letter to Number Converter (A1Z26)Convert letters to their alphabet position numbers, where A is 1 and Z is 26, or convert numbers back to letters.
- Hex CalculatorAdd, subtract, multiply and divide hexadecimal, binary, octal or decimal numbers, and apply bitwise AND, OR and XOR. Results in all four bases.
- Chmod CalculatorBuild Unix file permissions by ticking read, write and execute for owner, group and others. Get the octal number, symbolic notation and chmod command.
- IEEE 754 Floating Point ConverterConvert a decimal number to its IEEE 754 single and double precision representation: sign, exponent and mantissa bits, hex value and the exact stored number.
- Subnet CalculatorCalculate the network address, broadcast address, host range, subnet mask and number of hosts for any IPv4 address and CIDR prefix.
💯 Percent and Business Math
Percentages, percent change, discounts, profit margin, break-even and tips.
- Percentage CalculatorSolve the three basic percentage problems: what is X percent of Y, X is what percent of Y, and X is Y percent of what number.
- Percent Change CalculatorCalculate percentage increase or decrease between two numbers, or increase and decrease a number by a percentage.
- Discount CalculatorCalculate the sale price and savings from a percent off discount. Supports a second stacked discount and sales tax at a rate you enter.
- Profit Margin and Markup CalculatorCalculate profit margin, markup and profit from cost and selling price, or find the selling price needed for a target margin or markup.
- Break-Even CalculatorFind the break-even point in units and revenue from fixed costs, price per unit and variable cost per unit, with an optional profit target.
- Tip CalculatorCalculate a tip and the total bill, and split it evenly between any number of people.
🧮 Math and Statistics
Ratios, fractions, averages, factors, rounding, quadratics and probability.
- Ratio CalculatorSimplify a ratio, solve for a missing value in A : B = C : D, or split a total in a given ratio. Works with whole numbers and decimals.
- Proportion CalculatorSolve a proportion a/b = c/d for the missing value by cross-multiplication. Enter any three of the four numbers.
- Factor CalculatorFind all factors of a number, its factor pairs and its prime factorization. Also tells you whether the number is prime.
- GCF Calculator (Greatest Common Factor)Find the greatest common factor of two or more numbers, with the Euclidean algorithm steps and prime factorizations. Also gives the LCM.
- LCM Calculator (Least Common Multiple)Find the least common multiple of two or more numbers, with prime factorizations. Also gives the greatest common factor.
- Rounding CalculatorRound a number to the nearest whole number, tenth, hundredth, thousandth, ten, hundred or thousand. Exact decimal rounding with no floating point errors.
- Significant Figures CalculatorCount the significant figures in a number and round it to any number of significant figures, with scientific notation.
- Modulo CalculatorCalculate a mod n, the remainder after division, with the quotient. Handles negative numbers under both the mathematical and programming conventions.
- Long Division CalculatorDivide whole numbers and see every step of the long division, with the quotient, remainder, mixed number and decimal answer.
- Fraction CalculatorAdd, subtract, multiply and divide fractions and mixed numbers. The answer is simplified and shown as a fraction, a mixed number and a decimal.
- Simplify Fractions CalculatorReduce a fraction to its lowest terms and convert an improper fraction to a mixed number, with the greatest common factor used.
- Decimal to Fraction CalculatorConvert a decimal to a fraction in lowest terms, or a fraction to a decimal. Exact conversion for terminating decimals.
- Exponent CalculatorRaise a number to any power, including negative and fractional exponents. Gives exact answers for whole numbers and scientific notation for large results.
- Quadratic Formula CalculatorSolve ax² + bx + c = 0 with the quadratic formula. Gives real or complex roots, the discriminant, the vertex and the steps.
- Pythagorean Theorem CalculatorFind the missing side of a right triangle with the Pythagorean theorem. Also gives the area, perimeter and both acute angles.
- Slope CalculatorFind the slope, angle, percent grade, distance and midpoint between two points, and the equation of the line through them.
- Speed Distance Time CalculatorCalculate speed, distance or time from the other two. Works in mph, km/h, m/s and knots with any mix of units.
- Average CalculatorCalculate the average (mean) of a list of numbers, with the sum, count, median, mode, range and geometric mean.
- Median, Mode and Quartile CalculatorFind the median, mode, range, quartiles and interquartile range of a data set, with outlier fences and the sorted list.
- Standard Deviation and Variance CalculatorCalculate sample and population standard deviation and variance for a data set, with the mean, sum of squares and standard error.
- Weighted Average CalculatorCalculate a weighted average from values and their weights. Useful for grades, prices, ratings and any data where items count unequally.
- Z-Score CalculatorCalculate a z-score from a value, mean and standard deviation, with the percentile and the normal distribution probabilities above, below and between.
- Permutation and Combination CalculatorCalculate permutations (nPr) and combinations (nCr), with and without repetition, and factorials. Exact results for large numbers.
- Sample Size CalculatorCalculate the survey sample size needed for a given confidence level and margin of error, with an optional finite population correction.
📐 Geometry
Area, volume and surface area of circles, triangles, cylinders, spheres and more.
- Circle CalculatorCalculate the radius, diameter, circumference and area of a circle from any one of them.
- Triangle Area CalculatorCalculate the area of a triangle from base and height, from three sides with Heron's formula, or from two sides and the angle between them.
- Rectangle CalculatorCalculate the area, perimeter and diagonal of a rectangle or square from its length and width.
- Trapezoid Area CalculatorCalculate the area of a trapezoid from its two parallel sides and height, with the median line.
- Hexagon and Regular Polygon CalculatorCalculate the area, perimeter, apothem and angles of a regular hexagon, pentagon, octagon or any regular polygon from its side length.
- Cylinder Volume CalculatorCalculate the volume and surface area of a cylinder from its radius or diameter and height, with the result in liters and gallons.
- Sphere Volume CalculatorCalculate the volume and surface area of a sphere from its radius or diameter.
- Cone Volume CalculatorCalculate the volume, slant height and surface area of a right circular cone from its radius and height.
- Box Volume Calculator (Rectangular Prism)Calculate the volume, surface area and space diagonal of a box, cube or rectangular prism from its length, width and height.
- Pyramid Volume CalculatorCalculate the volume, slant heights and surface area of a rectangular or square pyramid from its base and height.
- Surface Area CalculatorCalculate the surface area of a cube, box, cylinder, sphere, cone or square pyramid, with the volume of the same shape.
🎯 Auto, Sports and Everyday
Gear ratios, tire sizes, sleep cycles, gestation dates, sports stats and game settings.
- Gear Ratio CalculatorCalculate gear ratio from tooth counts with output speed and torque, or find vehicle speed from engine RPM, axle ratio and tire diameter.
- Engine Displacement CalculatorCalculate engine displacement in cc, liters and cubic inches from bore, stroke and number of cylinders.
- Power to Weight Ratio CalculatorCalculate power to weight ratio in hp per pound, hp per ton, watts per kilogram and pounds per horsepower for cars, motorcycles and cyclists.
- Tire Size CalculatorCalculate tire diameter, sidewall height, circumference and revolutions per mile from a metric tire size, and compare two sizes with the speedometer difference.
- Sleep Cycle CalculatorFind the best time to go to bed or wake up based on 90-minute sleep cycles, so you wake at the end of a cycle and not in the middle of deep sleep.
- Animal Gestation CalculatorCalculate the due date for cows, horses, goats, sheep, pigs, dogs, cats and rabbits from the breeding date, with the normal range.
- ERA CalculatorCalculate earned run average (ERA) and WHIP for baseball and softball pitchers from earned runs, innings pitched, hits and walks.
- Batting Average CalculatorCalculate batting average, on-base percentage, slugging percentage and OPS for baseball and softball from at-bats, hits, walks and extra-base hits.
- Winning Percentage CalculatorCalculate winning percentage from wins, losses and ties, and see how many more wins are needed to reach a target percentage.
- Mouse Sensitivity ConverterConvert mouse sensitivity between Valorant, CS2, Apex Legends, Overwatch 2, Fortnite and other games, with eDPI and cm per 360.
- Nether Portal CalculatorConvert Minecraft Overworld coordinates to Nether coordinates and back, so linked portals line up. One block in the Nether equals eight in the Overworld.
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