# Crawl Ratio Calculator

URL: https://speedycalculator.com/calculators/physics/crawl-ratio/
Last updated: 2026-10-30

> The crawl ratio calculator finds the overall gear reduction of an off-road vehicle in its lowest gear – first gear × transfer case low range × axle ratio – and the crawl speed at a given engine rpm.

## Inputs

- First gear ratio
- Transfer case low range ratio
- Ring gear teeth
- Pinion teeth
- Engine speed (rpm)
- Tyre diameter (in, mm, cm, ft, m)

## Results

- Axle ratio
- Crawl ratio
- Crawl speed at this rpm

## Formula

```
Crawl ratio = first gear ratio × transfer case low ratio × axle ratio (ring teeth / pinion teeth)
```

## Explanation

Off-roaders want a high crawl ratio to climb rocks slowly with control. Stock 4×4s are around 40:1; serious rock crawlers exceed 100:1.

### How to use the Crawl Ratio Calculator

- **First gear ratio**
- **Transfer case low range ratio**
- **Ring gear teeth**
- **Pinion teeth**
- **Engine speed (rpm)**
- **Tyre diameter**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the gear ratios (or the ring and pinion tooth counts) and optionally the engine speed and tyre diameter to see the crawl speed.

### Inputs explained

FieldWhat to enterFirst gear ratioA numberTransfer case low range ratioA numberRing gear teethA numberPinion teethA numberEngine speed (rpm)A numberTyre diameterUnits: in, mm, cm, ft, m

### What each result means

- **Axle ratio** = [Ring gear teeth]÷[Pinion teeth]
- **Crawl ratio** = [First gear ratio]×[Transfer case low range ratio]×[Ring gear teeth]÷[Pinion teeth]
- **Crawl speed at this rpm** = [Engine speed (rpm)]÷60÷[Crawl ratio]×pi×[Tyre diameter]

### Example values

How the main result changes when **First gear ratio** changes and everything else stays at the example values above:

First gear ratioCrawl ratio (:1)222.3333.46444.61555.76666.91889.22

## Worked example

Inputs — First gear ratio: 4; Transfer case low range ratio: 2.72; Ring gear teeth: 41; Pinion teeth: 10; Engine speed (rpm): 800; Tyre diameter: 33 in.

Results — Axle ratio = 4.1 :1; **Crawl ratio = 44.61 :1**; Crawl speed at this rpm = 2.834 km/h.

## Key terms

- **Axle ratio**: Ring gear teeth divided by pinion teeth.

## FAQ

**What is a good crawl ratio?**
50–70:1 for a capable trail vehicle; 100:1+ for rock crawling.

**Is higher always better?**
Very high ratios can make the vehicle too slow on easy trails.

**How do I increase it?**
Lower axle gears, a lower transfer case, or a transmission with a deep first gear.

**Do tyres affect crawl ratio?**
No, but larger tyres raise the crawl speed.


## Sources

- [OpenStax – University Physics Volume 1](https://openstax.org/details/books/university-physics-volume-1)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)