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Calculate board feet for lumber from thickness, width, length and quantity across several boards, with total cost at a price per board foot and the equivalent in cubic metres. Free and private.

Estimate the cooling or heating needs of your room or house with our BTU calculator. Calculate exact requirements based on size, insulation, and climate.

Estimate the volume and weight of concrete needed for slabs, columns, stairs, and more. Get precise bag counts and truck delivery estimates.

Calculate the drywall sheets, screws, joint tape and joint compound for a room from its length, width and ceiling height, less doors and windows, with a waste allowance. Metric and imperial. Free.

Work out how many posts, sections, rails and pickets a fence needs from its length, post spacing, gates and board width, in metric or imperial. Use it to plan and price a fencing job. Free.

Calculate flooring for one or more rooms: total area, a waste allowance, how many packs or boxes to buy, what is left over and the cost. Works for laminate, vinyl, hardwood and tile in metric or imperial. Free.

Work out what size generator you need by listing your appliances with their running and starting watts. Adds the running load and the biggest starting surge, leaves headroom and suggests a standard size. Free and private.

Calculate how much gravel you need for a driveway or path in cubic yards, cubic feet, and tons.

Add up the R-values of your wall or ceiling assembly's layers to find its total R-value, then estimate heat loss for a given area and temperature difference.

Calculate how much mulch you need for your garden beds in cubic yards, cubic feet, and standard 2 cu ft bags.

Calculate how many gallons of paint you need for a room based on its dimensions, number of coats, and paint coverage per gallon.

Calculate how many gallons your pool holds from its dimensions -- supports rectangular and circular/round pools.

Convert roof pitch (like 6:12), angle in degrees and percent slope in any direction, then get rafter length with overhang, ridge height and roof surface area from your plan area. Metric and imperial. Free.

Accurately estimate your total roof area and the necessary amount of materials needed, including roofing squares, bundles of shingles, and recommended overage.

Accurately estimate the square footage and total cost of materials for a variety of common shapes, including rectangles, circles, triangles, and more.

Accurately calculate the exact dimensions for stairs including total run, stringer length, number of steps, and angle of inclination.

Estimate the total number of tiles necessary to cover a floor, roof, or wall, including calculations for grout gaps, overlaps, and total box costs.

Project a car's value year by year with a bigger first-year drop, or work out the average yearly depreciation rate from its price and current value. Free.

Estimate the cost of charging your electric vehicle from your battery size, charge level, and electricity rate -- and compare the cost per mile against a gas car.

Estimate the fuel needed and total cost for a trip based on distance, fuel efficiency, and price per gallon or liter.

Calculate your vehicle's fuel efficiency (MPG or L/100km) from the distance traveled and fuel used, plus your cost per mile or kilometer.

Estimate engine horsepower two ways — from quarter-mile trap speed and vehicle weight, or from torque and engine RPM.

Calculate your mileage reimbursement or tax deduction using the standard mileage rate for business, medical, moving, or charitable driving.

Calculate speed from distance and time, with instant results in mph, km/h, m/s, and knots.

Compare two tire sizes (e.g. 225/50R17) to see the difference in diameter, circumference, revolutions per mile, and speedometer accuracy.

Estimate battery runtime from capacity (mAh, Ah or Wh), load (mA, A or W), usable capacity and an active/sleep duty cycle, with average current and days of life. Free.

Convert power and voltage ratios to decibels and back, add sound levels correctly (60 dB plus 60 dB is 63 dB), and find how sound level falls with distance at 6 dB per doubling. Free and private.

Calculate density from mass and volume, with instant results in kg/m³, g/cm³, and lb/ft³.

Free dilution calculator using C1V1 = C2V2. Find the stock volume, final volume or concentrations in M, mM, mg/mL or %, see how much diluent to add, and plan serial dilutions.

Free electrical power calculator. Convert between watts, volts and amps for DC, single-phase and three-phase AC, with power factor, apparent and reactive power, resistance and horsepower.

Estimate the energy consumption and running cost of any electrical appliance based on its wattage, daily usage, and your electricity rate.

Free ideal gas law calculator. Solve PV = nRT for pressure, volume, amount of gas or temperature with units such as atm, kPa, bar, psi, litres, moles, Celsius and Kelvin.

Calculate the series resistor for one or more LEDs from supply voltage, forward voltage and current, rounded up to a standard E24 or E12 value, with actual current and resistor power rating. Free.

Convert mass between milligrams, grams, kilograms, metric tons, ounces, pounds, stone, and US tons instantly.

Calculate the molarity of a solution from solute mass, molar mass, and solution volume — a core calculation for chemistry lab work.

Calculate the molecular weight (molar mass) of any chemical formula, including compounds with parentheses like Ca(OH)2.

Solve for voltage, current, resistance, or power using Ohm's Law — enter any two known values and calculate the rest.

Free projectile motion calculator. Enter launch speed, angle and height to get the range, maximum height, time of flight, impact speed and the best launch angle, with a drawn trajectory. Earth, Moon, Mars or Jupiter gravity.

Calculate the time constant (tau) of an RC or RL circuit from the resistor and capacitor or inductor, the -3 dB cutoff frequency, the time to reach 63, 90, 95 and 99 percent, and the voltage or current after a chosen time.

Decode 4-band or 5-band resistor color codes into resistance value and tolerance, instantly and accurately.

Estimate how many years it takes for a home solar panel system to pay for itself through electricity bill savings, and project 25-year lifetime savings.

Calculate the output of a resistor voltage divider from Vin, R1 and R2, or solve for the missing resistor for a target Vout and pick the nearest standard E24 or E12 value. Shows current and power. Free.

Calculate voltage drop and percentage drop across a wire run based on wire gauge, material, distance, current, and circuit voltage.

Convert weight between kilograms and pounds, and see what you'd weigh on the Moon, Mars, Jupiter, and other planets based on their gravity.

Find the smallest AWG copper or aluminium wire for a load current, run length and allowed voltage drop, with the actual drop, heat loss and current rating. Metric or imperial. Free.

Calculate the dew point from air temperature and relative humidity using the Magnus formula, and see how muggy it will actually feel.

Calculate the heat index — the "feels like" temperature from air temperature and relative humidity — using the NWS Rothfusz regression.

Find the Moon's phase, percentage illuminated and age for any date and time, with a picture of the Moon and the dates of the next new moon, first quarter, full moon and last quarter. Free.

Calculate sunrise, sunset, solar noon, day length and civil, nautical and astronomical twilight for any date and location using NOAA solar equations, in your chosen time zone. Free.

Calculate wind chill — the "feels like" temperature from wind speed and air temperature — using the official NWS formula.

Count the number of days between two dates or calculate a future/past date. Includes options for business days, weekends, and holidays.

Find the day of the week for any historical or future date. Discover fascinating trivia and facts about every day of the week.

Free hours calculator to find the exact number of hours, minutes, and decimal hours between two times or dates. Instant calculation for timesheets, payroll, shifts, and schedules.

Free military time converter. Convert 12-hour AM/PM times to 24-hour and military time and back, with a full conversion chart from 0000 to 2300.

Find the best bedtime or wake-up time based on 90-minute sleep cycles, so you wake up feeling rested instead of groggy.

Calculate the exact time difference between two times or dates. Get results in hours, minutes, and seconds with our precise duration tool.

Convert time between different global time zones with our easy-to-use calculator. Understand UTC offsets, GMT, and daylight saving time.

Free week number calculator. Find the ISO 8601 week number of any date, the US week number, the day of the year and quarter, or list the Monday-to-Sunday dates of any ISO week.

Free baker's percentage calculator. Turn a bread or pizza formula into gram weights for any batch size, or turn your recipe weights into baker's percentages and hydration.

Find your cat’s age in human years and its life stage: kitten, junior, prime, mature, senior or geriatric. Based on the common chart of 15 human years for the first year, 24 for the second and 4 for each year after. Free and private.

Convert cups, tablespoons, teaspoons and millilitres to grams and back for 20 common baking ingredients, from flour and sugar to butter, honey and oil. Free and private.

Free depth of field calculator for photographers. Enter focal length, aperture, subject distance and sensor size to get the near and far limits of sharp focus, total depth of field and hyperfocal distance.

Roll virtual dice online — choose the number of dice and sides (d4 to d100) and get instant results with the total.

Convert your dog's age to human years using the size-based chart, the epigenetic formula 16 ln(age) + 31 and the classic 7x rule, with the life stage for your dog's size. Free.

Calculate exposure value (EV and EV100) from aperture, shutter speed and ISO, see the equivalent shutter speed at every full-stop aperture, and find the longest exposure before stars trail with the 500 rule and the NPF rule. Free and private.

Free Female Delusion Calculator: estimate what share of U.S. men meet height, income, age-range, and BMI standards.

Calculate Gross Domestic Product (GDP) using the expenditure approach — consumption, investment, government spending, and net exports.

Calculate your golf score differential from your score, course rating, and slope rating — the building block of the USGA Handicap Index.

Convert height between feet and inches, centimeters, and meters instantly, in either direction.

Free Male Delusion Calculator: estimate the share of U.S. women meeting BMI, height, income, and age standards.

Free pizza size calculator. Compare up to four pizza sizes and prices by area and price per square inch or per 100 cm², find the best deal, and see how many small pizzas equal one large.

Free print size calculator. Convert between image pixels, DPI and print size in inches or centimetres, see the largest good-quality print and check standard sizes such as 4x6, 8x10, A4 and A3.

Paste a recipe's ingredients and scale them to a new number of servings, with fractions handled, units tidied (4 tsp becomes 1 1/3 tbsp) and optional US or metric conversion. Free.

Convert numbers to Roman numerals or Roman numerals back to numbers, instantly and accurately, for values from 1 to 3,999.

Find a screen's width, height and area from its diagonal and aspect ratio, or its diagonal and ratio from a width and height, plus pixel density (PPI) and dot pitch from the resolution. Free.

Convert shoe sizes between US Men's, US Women's, UK, EU, and foot length in centimeters — a handy reference for international shopping.

Calculate the tip amount, total bill, and per-person split for any bill amount and tip percentage.

Free video file size calculator. Work out how big a 1080p or 4K video will be from its bitrate and length, the bitrate needed to hit a file size, or how many minutes fit on a card, in MB, GB and GiB.