Please note: these formulas are for estimating only. Contrary to popular belief, using this site will not increase your horsepower.

Here is a list of formulas:[back to top] •Rear Gear Ratio = (Tire Diameter * RPM) / (Trans Ratio * MPH * 336) •Tire Diameter = (Trans Ratio * MPH * 336 * Rear Gear Ratio) / (RPM) •RPM = (Trans Ratio * MPH * 336 * Rear Gear Ratio) / (Tire Diameter) •Trans Ratio = (Tire Diameter * RPM) / (Rear Gear Ratio * MPH * 336) •MPH = (RPM * Tire Diameter) / (336 * Rear Gear Ratio * Trans Ratio) •Tire Diameter (inches) = (((section width * profile) / 2540) + (wheel diameter / 2)) * 2 •HorsePower = TORQUE * RPM / 5252 •TORQUE = (5252 * HP) / RPM •1 Liter = 61.02374 Cubic Inches •Displacement (in^2) = Number Of Cylinders * 3.141592653589 * (Bore/2)^2 * Stroke •HP from MPH (1/4 mile) = WEIGHT * (MPH/234)^3 •HP from ET (1/4 mile) = WEIGHT * (5.825/ET)^3 •ET from HP (1/4 mile) = (WEIGHT / HP)^.333 * 5.825 •HP from cylinder head intake flow = CFM x 0.2575 x number of cylinders •1/4 mile ET = 1/8 mile ET x 1.5832 (prestage.com) •1/8 mile ET = 1/4 mile ET / 1.5832 (prestage.com) •piston speed in fpm = stroke in inches x rpm / 6 •rpm = piston speed in fpm x 6 / stroke in inches •bhp loss = elevation in feet / 1000 x 0.03 x bhp at sea level •theoretical cfm = rpm x displacement / 3456 •volumetric efficiency = acutal cfm / theoretical cfm x 100 •street carb cfm = rpm x displacement / 3456 x 0.85 •racing carb cfm = rpm x displacement / 3456 x 1.1->Formulas for g force & weight transfer•drive wheel torque = flywheel torque x trans gear x final drive x 0.85 •wheel thrust = drive wheel torque / rolling radius •g (force) = wheel thrust / weight •weight transfer = weight x cg height / wheelbase x g •lateral acceleration = 1.227 x radius / time^2 •lateral weight transfer = weight x cg height / wheel track x g •centrufugal force = weight x g->Formulas for shift points•rpm after shift = ratio shift into / ratio shift from x rpm before shift •driveshaft torque = flywheel torque x transmission ratio->Formulas for weight distribution•percent of weight on wheels = weight on wheels / overweight x 100 •increased weight on wheels = [ distance of cg from wheels / wheelbase x weight ] + weight->Formulas for center of gravity•cg location behind front wheels = rear wheel weights / overall weight x wheelbase •cg location off-center to heavy side = track / 2 - [ weight on light side / overall weight ] x track •cg height = [ level wheelbase x raised wheelbase x added weight on scale / distance raised ] x overall weight Check out Prestage.com for more useful formulas. email me at aaronmurray@msn.com if you have any formulas you would like to see added (as a calculator) or if you have any suggestions.