The calculation, without hidden assumptions
Engine RPM reaches the road through two reductions—the selected transmission gear and final drive—then through tire circumference. This owner solves either road speed or engine RPM and keeps the combined ratio visible, making it useful for cruise checks and drivetrain comparisons without pretending to predict real top speed.
How to use this calculator
Enter the selected transmission gear ratio, final drive and loaded tire diameter.
Choose whether to solve road speed from RPM or RPM from road speed.
Treat the result as geometric drivetrain speed and compare scenarios rather than as a guaranteed vehicle top speed.
Where people use it
- •Estimating highway cruise RPM
- •Comparing final-drive changes
- •Checking theoretical speed at a shift RPM
Example: 0.80 top gear with a 3.55 axle
The combined reduction is 2.84:1. With the same tire, changing either the transmission ratio or axle ratio changes engine RPM at every road speed in direct proportion.
What the result does not assume
- •The 336 formula is a conventional inch/mph approximation. Tire loaded radius and real rolling circumference can differ from nominal diameter.
- •Converter or clutch slip, wheelspin, tire growth, aerodynamic drag and engine power are excluded, so calculated speed is not a guaranteed achievable top speed.
Frequently asked questions
What is overall gear ratio?+
For this calculation it is the selected transmission gear ratio multiplied by the final-drive or axle ratio.
Do larger tires lower cruise RPM?+
For unchanged gearing and road speed, a larger rolling diameter generally lowers engine RPM.
Can this predict top speed?+
It predicts geometric speed at an RPM. Real top speed may be lower because of power, drag, traction or rev limits.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
Tire Size Calculator — Compare Diameter, Clearance & Speedometer Error
Compare two P-metric tire sizes side by side for sidewall, diameter, circumference, axle clearance and theoretical speedometer error.
OpenRatio Calculator
Simplify integer or decimal ratios, solve a missing proportion value, scale a ratio, and split a total into proportional shares with visible working.
OpenSpeed Converter
Convert nonnegative speed between meters per second, kilometers per hour, miles per hour, knots and feet per second.
OpenDew Point Calculator — Temperature & Relative Humidity
Dew point marks the temperature where air reaches saturation. Free deterministic calculator with worked formula, editable assumptions, visible steps and practical examples for quick browser-based checks.
OpenHeat Index Calculator — Temperature & Humidity
Estimate apparent heat from air temperature and relative humidity using the standard regression. Free deterministic calculator with worked formula, editable assumptions, visible steps and practical examples for quick browser-based checks.
OpenWind Chill Calculator — Temperature & Wind Speed
Estimate cold-weather apparent temperature from air temperature and wind speed. Free deterministic calculator with worked formula, editable assumptions, visible steps and practical examples for quick browser-based checks.
OpenDensity Calculator — Mass ÷ Volume
Calculate density directly from mass and volume with the formula and units visible. Free deterministic calculator with worked formula, editable assumptions, visible steps and practical examples for quick browser-based checks.
OpenMolarity Calculator — Moles & Solution Volume
Calculate molar concentration from amount of solute and final solution volume. Free deterministic calculator with worked formula, editable assumptions, visible steps and practical examples for quick browser-based checks.
OpenMore in this calculator collection
Browse nearby calculators in the same topic cluster so related pages reinforce each other instead of sitting as isolated URLs.
Free publisher widget
Put this calculator on your website
Give readers the live calculator without rebuilding the math. Copy the responsive embed in one click, or customize width, height, border and corner radius before publishing. The branded MAXScanner attribution stays visible.
Embed HTML
Paste this code into your page. Tap the code box to select it manually.
Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.