Crawl Ratio Calculator for Any 4x4 (With Tire Size Effect)
Crawl ratio is your lowest gearing: first gear × transfer-case low range × axle ratio. A JL Wrangler Rubicon with the 8-speed automatic is 4.71 × 4.00 × 4.10 = 77.2:1, the figure Jeep published. Put 37-inch tires on it and the effective ratio drops to about 69 (a 33-inch stock tire is assumed in this example). Enter your own numbers below to see your crawl ratio, the effect of a tire change and your speed at idle-range RPM.
Crawl ratio calculator
Crawl ratio calculator: first gear × low range × axle ratio, with an optional tire-size effect.
From your transmission spec sheet or service manual, for example 4.71.
For example 2.72 (Jeep Command-Trac and Selec-Trac) or 4.00 (Rock-Trac).
Metric (265/70R17) or flotation (35x12.50R17), or a measured height like 33.6. Leave both tire boxes empty to skip tires.
Own a Bronco? Use the Bronco crawl ratio calculator, which covers its transmission, transfer case and axle combinations. More free tools: see all our off-road calculators.
How it works
Crawl ratio is the total gear reduction between the engine and the wheels in the lowest gear combination. As California Jeeper’s crawl ratio guide puts it: Crawl Ratio = First Gear Ratio × Transfer Case Low Range Ratio × Axle Ratio. A 50:1 ratio means the engine turns 50 times for each turn of the tires.
Crawl speed uses the standard gear-ratio formula, mph = RPM × tire diameter ÷ (gear ratio × 336), as given in Quadratec’s tire and gear ratio guide, with the crawl ratio as the gear ratio. The tire effect works the same way as in our regear calculator: a taller tire covers more ground per turn, so the effective ratio falls in proportion to tire height. The effective-ratio figure is a convention we use for comparing before and after, not a number manufacturers publish.
Published Jeep Wrangler JL ratios
| Wrangler JL setup | Published figure | Source |
|---|---|---|
| Rubicon, 8-speed automatic | Crawl ratio 77.2:1 (4.7:1 first gear, 4.1:1 final drive, 4:1 4LO) | Jeep 2018 press kit |
| Rubicon, 6-speed manual | Crawl ratio 84.2:1 | Jeep 2018 press kit |
| Sport and Sahara, Command-Trac | 2.72:1 low range, 3.45 rear axle ratio | Jeep 2018 press kit |
| Rubicon 392 (2024), Selec-Trac | 2.72:1 4LO, 4.56 axle ratio | Jeep 2024 press release |
| 2024 Rubicon, best case | Crawl ratio up to 100:1 | Jeep 2024 press release |
Jeep rounds the 8-speed’s first gear to 4.7:1; using 4.71 reproduces the published 77.2:1 (4.71 × 4.00 × 4.10 = 77.25). The manual’s first-gear ratio is not given in that press kit, so we did not preset it. We also left out presets for other vehicles until we can confirm their ratios from the maker’s own spec sheet. For those, type the three ratios from your owner’s manual or service manual. To see how Jeep’s transfer cases differ, read Command-Trac, Rock-Trac or Selec-Trac.
Going bigger on tires? Check the tire size calculator and the gear ratio for 37s on a Wrangler JL, or start with what gear ratios mean in off-roading.
FAQ
Do bigger tires change my crawl ratio?
The gear ratios stay the same, but each engine revolution moves you farther, so the effective ratio drops. The calculator shows this as a percentage. Regearing the axles is the usual fix.
Where do I find my first gear ratio?
Check your owner’s manual, the transmission maker’s spec sheet or the factory service manual for your exact model year and transmission. Ratios differ between transmissions and sometimes between model years.
I'm Suryashankar Dasgupta, the founder of Off-Road Handbook. I've been off-roading for years in the USA, including California and Texas, and have ridden mountain and desert terrain abroad. I've also driven a Jeep Compass for more than seven years, so I know the day-to-day side of Jeep ownership first-hand, from the Uconnect screen to the warning lights. Every guide here is researched from manufacturer owner's manuals, NHTSA recall and service-bulletin records and other trusted sources, checked against them before it is published, and corrected when we find a mistake. You can read how we work in our editorial policy: https://offroadhandbook.com/editorial-policy/
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