Online Calculators & Tools

Finds your western star sign from a birth date, with its element, quality, ruling planet and opposite sign, and says when a date sits on a boundary.

Converts VA to watts at a power factor and back again, with the reactive power in var, the phase angle and the current for a single or three phase supply.

Estimates how long a UPS or inverter battery bank holds a load, from the bank capacity in amp hours, the system voltage, inverter efficiency, depth of discharge and Peukert exponent.

Works out how a tire's gauge pressure changes with temperature or altitude, using the gas law and the standard atmosphere, in psi, bar and kPa.

Estimates a tattoo price from the shop hourly rate and minimum charge, the size of the design, and detail and placement factors you can change yourself.

Swimming pace per 100 and per 50 in both yards and metres, from a swim you have done or a target pace you mean to hold, with cumulative splits.

Turns a measured foot length in centimetres or inches into US men's, US women's, UK, EU and Mondopoint shoe sizes on a named conversion basis.

Turns a set's weight, reps and RPE into a percentage of your one rep max, and works the other way to give the weight for a target RPE.

Counts a whole roofing load: squares, shingle bundles, underlayment rolls, ice and water shield, starter strip, hip and ridge cap, drip edge, valley metal and nails.

Counts the trusses a building needs from its length and spacing, and works out the run, rise, slope and chord lengths of a common truss.

Counts the rebar in a slab grid: bars each way from the spacing and edge cover, total linear feet, weight, and how many stock bars to buy with lap splices.

Scores the Revised Cardiac Risk Index from its six criteria and returns the point count and the risk class, without attaching a percentage the sources disagree on.

Estimates quarter mile ET and trap speed from race weight and horsepower using the Hale, Fox and Huntington formulas, and works backwards from a timeslip.

Prostate volume in cc from the three dimensions on an ultrasound or MRI report, using the ellipsoid formula, plus PSA density when a PSA value is entered.

Works out how much potting mix a round pot, rectangular planter or window box takes, in litres, cubic feet, dry quarts and whole bags.

Turns a waist and inseam measurement into a pants size: the US number, the letter, the EU and UK numbers and the W by L tag denim is sold by.

Works out the osmolarity of a solution in mOsm/L from the molar concentration of each solute and the number of particles it dissociates into.

Multiplies decimals and shows the working: the whole-number multiplication in a column, how many decimal places the factors carry, and where the point goes.

Turns a coverage area and depth into cubic yards, tons and bag counts for decorative landscape rock, using the density of the rock you actually chose.

Works out your K/D and KDA from kills, deaths and assists, and how many more matches it takes to drag a lifetime ratio up to a target.

Turns a fasting protocol and one meal time into clock times: when the eating window opens and closes, when the fast ends, and the halfway point.

Works out a heating and cooling load from the building envelope itself: wall and ceiling areas, R-values, window U-values, air changes, solar gain and internal gains.

Adds, subtracts, multiplies and divides hexadecimal numbers, and runs AND, OR, XOR, NOT and the shifts, with every answer given in hex, decimal and binary.

Daily calorie needs from the revised 1984 Harris-Benedict equations, with the original 1919 figures and Mifflin-St Jeor shown beside them.

Works out how much hardwood a floor takes: the square footage, the waste allowance, the number of boxes to buy and the board and row count.

Prices a hardwood floor installed: boards plus waste, labour, sanding and finishing, fasteners, underlayment, removing the old floor and the trim.

Finds the date six calendar months after a birthday, the weekday it falls on, how far away it is, and the age reached on that day.

Turns your own weekly spend per adult into a monthly and yearly grocery budget for the household, counting teenagers and children separately.

Works out what a charge costs from the kWh added, your own electricity price and the charging loss, then compares the cost per mile against gasoline at a price and an MPG you enter.

Turns a file size and a connection speed into a transfer time, keeping megabits and megabytes straight and taking protocol overhead off the line rate.

Runs an asset through straight line, declining balance, double declining or sum of the years digits, and prints the full year by year schedule.

Works out the interest paid between any two payment numbers on an amortising loan, or across one year of it, with the principal and balances alongside.

Turns a volume in cubic feet into the square feet it covers at a depth you set, and back again, with square yards, square metres and cubic yards alongside.

Adds up countertop square footage run by run, counts the finished edge in linear feet, and prices both from the figures your fabricator quoted.

Prices a concrete pour from its dimensions: the yards actually ordered, the short-load charge on a small load, delivery, pump hire and placing labour.

Total to HDL and LDL to HDL cholesterol ratios, plus non-HDL cholesterol, from the numbers already on your lipid panel, with the usual reference bands.

Scores a pairing of two Chinese zodiac animals using the traditional harmonies, clashes and harms between the twelve branches, plus their fixed elements.

Works out how many battens fit a wall, the real gap between them once they divide evenly, the linear feet of lumber and the boards to buy.

Turns a battery capacity in mAh and a device load in mA into a runtime, with a derating factor, and works out the life of a duty cycled device that sleeps between wakes.

Works out the loan to value ratio on a car loan, the balance measured against what the vehicle is worth, and shows the negative equity and gap that sit above it.

Divides AST by ALT to give the De Ritis ratio, with the inverse, the band the figure falls in and each enzyme against your own laboratory's upper limit.

Finds the length of a circular arc from the radius and central angle, with the chord, the sector area and the segment area alongside it.

Tank volume, surface area, filter turnover and the ammonia and nitrate a stocking plan produces, worked out from the fish you actually intend to keep.

Converts a nominal interest rate and a compounding frequency into the annual percentage yield, runs the conversion backwards, and compares two accounts side by side.

Projects yearly mileage from two dated odometer readings, and shows whether a lease allowance will be blown and what the excess miles would cost.

Reduces the digits of a birth date to a single figure and shows the repeating sequence it makes, or breaks down a number you keep noticing.

Adds a column of figures and prints a tape with the running total on every line, plus the added and subtracted subtotals and an optional percentage.

Wet bulb temperature from air temperature and relative humidity using the Stull approximation, with the reverse reading for a sling psychrometer.