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
| Field | What to enter |
|---|---|
| First gear ratio | A number |
| Transfer case low range ratio | A number |
| Ring gear teeth | A number |
| Pinion teeth | A number |
| Engine speed (rpm) | A number |
| Tyre diameter | Units: 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 ratio | Crawl ratio (:1) |
|---|---|
| 2 | 22.3 |
| 3 | 33.46 |
| 4 | 44.61 |
| 5 | 55.76 |
| 6 | 66.91 |
| 8 | 89.22 |
Formula
Crawl ratio = first gear ratio × transfer case low ratio × axle ratio (ring teeth / pinion teeth)
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.
Frequently asked questions
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.