Calculators

Every calculator in one place — the everyday sums (percentage, tip, discount, tax, GPA, age) plus the scientific, statistics, drilling-engineering and electrical calculators.

• Percentage calculatorThe everyday percentage questions in one place — what is X% of Y, X is what percent of Y, the percentage…
• Tip & bill split calculatorEnter the bill, pick a tip percentage and split it between any number of people — see the tip, the total and…
• Discount, markup & margin calculatorThree everyday pricing sums in one: the discount (a % off → sale price and how much you save), the markup…
• Sales tax & VAT calculatorAdd sales tax / VAT to a net price to get the gross, or strip the tax out of a gross price to find the net —…
• GPA calculatorList your courses with a letter grade and the credit hours for each and get your weighted grade-point average…
• Age calculatorEnter a date of birth and get the exact age in years, months and days, the totals in months, weeks, days and…
• Time duration calculatorWork out how long there is between a start and end time — handling shifts that run past midnight and…
• Unit & date calculatorConvert length, weight, temperature, area, volume, speed, data and time — and work out the days between dates…
• Scientific & graphing calculatorA full scientific calculator — trig in degrees or radians, logs, powers, factorials, combinatorics and…
• Statistics calculatorPaste a column of numbers for full descriptive statistics — mean, median, mode, sample & population spread,…
• Mud Weight & HydrostaticsDrilling-fluid pressure maths — hydrostatic pressure, pressure gradient, equivalent mud weight (EMW),…
• Pump Output & CirculationMud-pump output and circulation maths — triplex and duplex output per stroke and flow rate, annular velocity,…
• Hole & Pipe VolumeHole, pipe and annular capacity and volume, open- and closed-end pipe displacement, and slug calculations.…
• Well Control Kill SheetWell-control kill-sheet maths — kill mud weight, formation pressure, initial and final circulating pressures,…
• Drillstring MechanicsDrillstring load maths — buoyancy factor and buoyed weight, margin of overpull, drill-collar weight for…
• Directional SurveyDirectional-survey maths — dogleg severity by the minimum-curvature method, the TVD/north/east step between…
• Bit HydraulicsBit-hydraulics maths — total flow area from nozzle sizes, nozzle velocity, bit pressure drop, hydraulic…
• Surge, Swab & TrippingTripping maths — hole-fill per stand, a simplified surge/swab pressure estimate, trip margin, and usable…
• Ohm's Law & PowerThe V·I·R·P wheel — enter any two of voltage, current, resistance and power and get the other two — plus DC,…
• Voltage DropWork out the voltage drop over a cable run — volts lost, drop as a percentage, the voltage left at the load,…
• Wire Size & AmpacityConvert conductor sizes between AWG/kcmil and mm², apply ambient-temperature and grouping derating to a…
• Circuit Load & Breaker SizeList the loads on a circuit or distribution board with their quantities and demand factors, and get the…
• Energy CostWork out what an appliance or circuit really costs to run — from its power rating and hours of use, from two…
• Transformer Sizing & RatioFull-load current on both sides of a transformer, the turns ratio including the delta/star √3 caveat, and the…
• Motor Full-Load CurrentFull-load current from a motor nameplate for DC, single- and three-phase supplies, with the NEC table value…
• Power Factor & CorrectionSolve the power triangle from any two of kW, kVA, kVAr and power factor, then size a correction capacitor…
• Lighting — Lux & LumensThe lumen method in three parts: how many lumens and luminaires a target illuminance demands, what an…