 Calculators

This is a collection of calculators that may be helpful to scooter enthusiasts.

 Fuel/Oil Mix Ratio Calculator Enter the amount of fuel and the desired mix ratio(__:1) and this calculator will tell you the amount of oil needed in both ounces and milliliters. Gallons of Fuel Ounces of Oil Desired Mix Ratio Milliliters of Oil
 Fuel/Oil Economy Calculator If you enter all the required fields, this calculator can tell you the fuel economy, fuel cost, oil cost for 2 strokes, and cost per mile for fuel and oil. If you are using this calculator for a 4 stroke you can leave the oil fields blank. MPG Miles Traveled Fuel Cost (Trip) Gallons of Fuel Used Oil Cost (Trip) Fuel Cost Per Gallon Fuel Cost Per Mile Oil Mix Ratio Oil Cost Per Mile Oil Cost Per Quart Total Cost Per Mile
Tire Diameter And Circumference

Enter the tire width(mm), aspect ratio, and wheel diameter(in) and this calculator will tell you the tire's diameter and circumference in inches and millimeters. Circumference in mm is often used to calibrate aftermarket speedometers.

 130/70P12 Width(mm) Aspect Ratio Wheel Diameter(in)
Width Diameter (in)
Aspect Ratio Diamter (mm)
Wheel Diameter Circumference (in)
Circumference (mm)
 Speed Calculator Enter tire circumference(in), final drive ratio(__:1), and engine RPM and this calculator will give you the maximum speed for that setup. This may be a bit inaccurate for CVT driven scooters. You would actually need to know the RPM that the clutch bell is turning to be completely accurate. This calculator can give you a good idea of max speed differences using different tire sizes, different gear ratios, or setups that rev a little different. Tire Circumference Final Drive Ratio Speed RPM
 Speedometer Tire Size Correction Calculator This calculator can help you improve the accuracy of speedometers that require a tire size input for calibration. Enter the current tire size in your gauge (usually circumference in mm). Then you will need to have a trip odometer reading from a ride as well as a known accurate mileage from the same ride (usually GPS info) to enter. The calculator will output a corrected tire size for the gauge based on your inputs. Current Tire Size Speedometer Mileage Corrected Tire Size Actual Mileage
 Displacement Calculator Enter the bore and stroke in millimeters and the number of cylinders and this calculator will tell you the displacement in both cubic centimeters and cubic inches. Bore Displacement (cc) Stroke Displacement (ci) # of Cylinders
 Piston Ring End Gap Calculator Enter the bore in millimeters and this calculator will tell you the compression ring end gaps in inches for two-stroke and four-stroke engines. Bore 4T Top Ring 4T Second Ring 2T Rings
 Compression Ratio Calculator Enter the volume of the cylinder and the volume of the combustion chamber and this calculator will tell you the compression ratio (referred to as secondary compression in 2 strokes). For multi-cylinder engines, just use the columes from one cylinder. If you wish to find the effective (corrected) compression ratio of a 2 stroke engine, enter the effective cylinder volume instead of the total cylinder volume. Don't forget to add the volume of the cylinder head gasket to the volume of the combustion chamber. You can find the head gasket's volume by using the displacement calculator above (enter the gasket's thickness in mm into the stroke field). You also need to take deck height and the piston (dished, flat, or domed) into account. Cylinder Volume Compression Ratio Combustion Chamber Volume
 Combustion Chamber Volume This calculator will tell you the combustion chamber volume necessary to achieve your desired compression ratio (__:1). If you are using a head gasket, remember that it's volume needs to be subtracted from the combustion chamber volume shown here to get a correct result. Desired Compression Ratio Combustion Chamber Volume Cylinder Volume
 Primary Compression Ratio Enter the crankcase volume(cc) and cylinder volume(cc) and this calculator will show you the primary compression ratio of a 2 stroke engine. Crankcase Volume Primary Compression Cylinder Volume
Degrees From TDC To Piston Position

This calculator allows you to convert crankshaft angle in degrees from TDC (Top Dead Center) to mm or inches from TDC. This is helpful for setting up many racing ignitions. You will need to know stroke in mm and connecting rod length in mm. Conrod length is measured center to center.

Degrees From TDC Distance (mm)
Stroke (mm) Distance (in)
Conrod Length (mm)
Piston Position to Degrees From TDC

This calculator allows you to convert piston position in mm from TDC to crankshaft angle in degrees from TDC (Top Dead Center). This is helpful for setting up many racing ignitions. You will need to know stroke in mm and connecting rod length in mm. Conrod length is measured center to center.

Distance From TDC (mm) Degrees From TDC
Stroke (mm)
Conrod Length (mm)
 1/4 Mile Calculator Enter 1/4 mile elapsed time (E.T.) in seconds and trap speed along with the vehicle weight with driver (lb) and this calculator will give you an estimate of horsepower and torqe to the wheel(s) as well as power to weight ratio (HP per lb). 1/4 Mile E.T. Horsepower (E.T. Method) 1/4 Mile Trap Speed Torque (E.T. Method) Vehicle Weight Horsepower (Trap Method) Engine RPM (Trap) Torque (Trap Method) Horsepwer (Average of ET and Trap Methods) Torque (Average of ET and Trap Mehods) Power To Weight Ratio (Average)