Crawl Ratio Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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The quickest way to trust a crawl ratio estimate is to see how the answer responds when an input changes. Mechanical design calculations become much more useful when you can see the exact ideal relationship behind the headline number and where real hardware can depart from it. The sections below show what this page calculates, how it does it, and where the simplified model stops.

What this calculator does

This calculator isolates the relationship between Transmission ratio (TG), Transfer gear ratio (TCG), Axle gear ratio (AGR) and crawl ratio. That makes it easier to see which input is controlling the result and to distinguish the headline quantity from secondary values shown underneath.

How to use it

For a clean calculation, enter Transmission ratio (TG), Transfer gear ratio (TCG), Axle gear ratio (AGR), Number of ring gear’s teeth, Number of pinion’s teeth exactly as defined by the labels and their units. Check the headline value, then scan the supporting metrics for a relationship that should obviously increase or decrease with one input; this is a fast way to catch an entry mistake.

How the calculation works

The headline crawl ratio is first-gear ratio × transfer-case ratio × entered axle ratio. Ring and pinion tooth counts are used only to show a supporting tooth-derived axle ratio; they do not replace the axle-ratio field in the headline calculation.

Example

Using the default drivetrain values (Transmission ratio (TG) = 4; Transfer gear ratio (TCG) = 2.72; Axle gear ratio (AGR) = 4.1; Number of ring gear’s teeth = 41), the page returns a crawl ratio of 44.608. If you change ring and pinion tooth counts without changing the axle-ratio field, the supporting tooth-derived ratio changes but the headline crawl ratio does not.

How to interpret the result

A larger crawl ratio means more overall gearing reduction between the engine and axle in this ideal product, which generally supports slower wheel speed and greater torque multiplication before losses. Compare vehicles only when the same definition and drivetrain stages are included.

Limitations and notes

The headline uses the entered axle-ratio field even when ring and pinion tooth counts are present; the tooth-derived axle ratio is only a supporting value. Tire deformation, torque-converter multiplication, clutch slip, and drivetrain losses are not part of the crawl-ratio product.