Travel & Vehicle Calculators
Free travel calculators for fuel economy (MPG), speed, distance and travel time, tire size and speedometer error, flight time, and road trip budgeting.
Travel & Vehicle Calculators - Fuel, Speed, and Trip Planning
Whether you are budgeting a road trip, checking a car’s real fuel economy, decoding a tire size, or working out flight time, these calculators turn everyday driving and travel questions into concrete numbers. Each one shows the formula and the working, so you learn the method as well as the answer.
Eight Travel Calculators
MPG Calculator - Works out miles per gallon, litres per 100 km, and km per litre from the distance you drove and the fuel you used. Add a fuel price to see the cost per mile and per kilometre. Handles both miles and kilometres and both US gallons and litres.
Boat Speed Calculator - Estimates a planing boat’s top speed from engine horsepower and running weight using Crouch’s formula (V = C times the square root of hp divided by weight). Choose a Crouch constant for your hull, from cruiser to racing catamaran, and read the result in knots, mph, and km/h.
Speed Calculator - Solves the speed, distance, and time relationship three ways: find average speed from distance and time, find distance from speed and time, or find travel time from distance and speed. Results in both mph and km/h, with time shown in hours and minutes.
Speedometer Gear Calculator - Shows how a change in tire diameter or axle gear ratio affects your speedometer reading. Enter the indicated speed and the old and new tire sizes (and gear ratios if changed) to see your true speed and the percentage error.
Tire Size Calculator - Decodes a tire size code like 225/45R17 into sidewall height, overall diameter, circumference, and revolutions per mile, and compares two sizes for a quick speedometer check.
Flight Time Calculator - Calculates flight time from distance and cruise airspeed, adjusted for headwind or tailwind, with results in hours, minutes, and groundspeed.
Road Trip Cost Calculator - Budgets a whole multi-day road trip by combining fuel, food, lodging, and miscellaneous costs into one total, with a full breakdown by category.
Fuel Pump Calculator - Calculates the minimum fuel pump flow rate an engine needs from target horsepower and BSFC, with an adjustable safety margin. Preset BSFC values for naturally aspirated, turbo/supercharged, and E85 setups, with results in L/hr (LPH), gal/hr, and lb/hr.
Why Fuel Economy and Speedometer Accuracy Matter
Real-world fuel economy is almost always different from the sticker figure, because it depends on driving style, load, terrain, and traffic. Measuring it tank by tank with the MPG Calculator reveals your true running cost. Tire and gear changes matter too: fitting larger tires makes the wheels turn fewer times per mile, so the speedometer reads slower than you are actually going. The Speedometer Gear Calculator quantifies that error so you can recalibrate or simply drive with the correction in mind.
Frequently Asked Questions
How do I calculate my car's MPG?
Divide the miles driven by the US gallons of fuel used. If you drove 300 miles on 12 gallons, that is 25 MPG. The MPG Calculator also converts to litres per 100 km and km per litre, and can show cost per mile.
How do I work out average speed?
Divide distance by time. Driving 150 miles in 2 hours 30 minutes is 150 divided by 2.5 = 60 mph. The Speed Calculator also finds distance from speed and time, or travel time from distance and speed.
Do bigger tires make the speedometer read wrong?
Yes. Larger-diameter tires travel further per revolution, so the speedometer reads lower than your actual speed. Fitting a 31-inch tire in place of a 28-inch one makes you about 11 percent faster than the dial shows. The Speedometer Gear Calculator gives the exact figure.
Is fuel economy better in MPG or litres per 100 km?
They measure the same thing in opposite directions: higher MPG is better, but lower litres per 100 km is better. The MPG Calculator shows both so you can compare figures quoted in either system.