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Works the air an engine needs in lb/min and the pressure ratio across the compressor, which together are the point you plot on a compressor map.

Works out engine horsepower from torque and RPM through the 5252 relation, turns power back into torque, and converts a wheel figure into a crank figure.

Work out how long a drive really takes: cruising speed, a traffic allowance, rest breaks, fuel stops, and the clock time you arrive across a time zone.

Work out what a tire change does to the final drive, the rpm and the speedometer, and which axle ratio puts the original gearing back.

Adds depreciation, fuel, insurance, servicing, tyres, tax and loan interest over a whole ownership period, then turns the total into a cost per year, per month and per mile.

Work out what driving to work costs over a full year in fuel, wear and parking, and set that total against a transit pass or a carpool share.

Works out 0-60 acceleration three ways: average g and distance from a time, the time from a distance and a speed, and an estimate from weight and horsepower.

Adds up a tow the way the invoice does: hook-up fee, billable miles, after-hours and winch-out surcharges, storage and tax, from the rates you were quoted.

Works out engine RPM from road speed, tire size, gear ratio and final drive, and runs the same chain backwards for road speed or the axle ratio you need.

Splits a fill between the E85 pump and the gasoline pump to hit a target ethanol content, and works out what a partial fill actually left in the tank.

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

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.

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

Find the carburetor CFM an engine needs from its displacement, peak rpm and volumetric efficiency, or the rpm a carburetor you already have can feed.

Costs a lease and a car loan over the same number of months, counting the equity left in a bought car against the payments and fees on a lease.

Net internal volume of a subwoofer enclosure from its outside dimensions, the sealed alignment it lands on, and the port length for a chosen tuning.

Estimates what an accident took off a car's resale value, using the 17c formula with its damage and mileage multipliers or a before-and-after comparison.

Static compression ratio from bore, stroke, chamber volume, gasket, deck clearance and piston dish, plus the dynamic ratio from intake valve closing.

Builds a vinyl wrap estimate from film, waste, fitting hours and extras at your own prices, or breaks a quote you already have into film and labour.

Does the towing arithmetic on ratings you read off your own vehicle: GCWR minus the loaded vehicle, payload against tongue weight, and the limit that bites first.

Turns engine output and vehicle weight into hp per pound, pounds per horsepower, hp per ton and watts per kilogram, and puts two vehicles side by side.

Prices the dealer's two offers against each other: the promotional low APR on the full price, or the cash rebate financed at your own bank's rate.

Work out the oil for a two-stroke mix at any ratio, check the ratio you actually poured, or find the fuel that matches a bottle of oil you already have.

Work out engine displacement from bore, stroke and cylinder count, in cc, litres and cubic inches, with an optional overbore for a block bored oversize.

Projects what a vehicle will be worth using the declining balance model, with a steeper first year, and works the rate back from a real resale value.

Converts wheel offset to backspacing and back, and compares two wheels to show how far the new one moves toward the fender or the suspension.

Monthly payment on a used car once sales tax, dealer fees, a down payment and a trade-in are folded in, plus a side-by-side of 36 to 72 month terms.

Adds fuel, tolls, lodging and food into one road trip budget, splits it per traveller, and compares the cost of driving against flying.

Work out miles per gallon from a tank of fuel, either from the miles you drove or from two odometer readings, with metric equivalents.

Works out the balance left on a car loan, the per diem interest, a payoff figure good for a set number of days, and whether you owe more than the car is worth.

Turn a tire size such as 225/45R17 into a real diameter, and compare two sizes to see the change in height, revolutions and speedometer reading.

Work out what fuel will cost for a trip from the distance, your vehicle economy and the pump price, in miles and MPG or kilometres and litres per 100 km.