Free calculator Tires, gears, rpm
Jeep Wrangler Tire Size and Gear Ratio Calculator
Enter your current tire size, the new size and your axle ratio, and this free calculator shows how far off the speedometer will be, what your gears now act like, the ratio that restores the factory feel, and engine rpm and crawl ratio for your Wrangler's gearbox. The gearbox and axle figures are from Jeep's own specification sheets.
Bigger tires change more than the look of a Wrangler. A taller tire covers more ground on every turn, so the speedometer reads low, the engine turns slower at a given speed, and the Jeep pulls as if it had taller gears. This calculator puts numbers on each of those for your tires and your axle ratio.
It knows the first and top gear ratios of the Wrangler gearboxes Jeep has published, from the YJ’s five-speed to the JL’s eight-speed automatic, so the highway rpm and crawl ratio are for your drivetrain. Copy the link to save a setup or send it to the shop doing the work.
RPM charts
Engine rpm at 65 mph by tire size and gear ratio
Top gear with the torque converter locked. Read across a row to see what a regear does for one tire size, or down a column to see what bigger tires do to one ratio.
JL with the 8-speed automatic (0.67 top gear)
| Tire | 3.45 | 3.73 | 4.10 | 4.56 | 4.88 |
|---|---|---|---|---|---|
| 31 in | 1,629 | 1,761 | 1,936 | 2,153 | 2,304 |
| 32 in | 1,578 | 1,706 | 1,876 | 2,086 | 2,232 |
| 33 in | 1,530 | 1,655 | 1,819 | 2,023 | 2,165 |
| 35 in | 1,443 | 1,560 | 1,715 | 1,907 | 2,041 |
| 37 in | 1,365 | 1,476 | 1,622 | 1,804 | 1,931 |
JK with the 5-speed automatic (0.83 top gear)
| Tire | 3.21 | 3.73 | 4.10 | 4.56 | 4.88 |
|---|---|---|---|---|---|
| 31 in | 1,878 | 2,182 | 2,398 | 2,667 | 2,855 |
| 32 in | 1,819 | 2,114 | 2,323 | 2,584 | 2,765 |
| 33 in | 1,764 | 2,050 | 2,253 | 2,506 | 2,682 |
| 35 in | 1,663 | 1,933 | 2,124 | 2,363 | 2,528 |
| 37 in | 1,573 | 1,828 | 2,009 | 2,235 | 2,392 |
Tire size chart
Wrangler tire sizes and their height in inches
Height worked out from the size on the sidewall: the wheel diameter plus twice the sidewall, where the sidewall is the width times the aspect ratio. Factory sizes are from Jeep's specification sheets. Real tires run a little under or over the nominal figure.
JL factory sizes, 2018 on
| P245/75R17 | 31.5 in |
|---|---|
| P255/70R18 | 32.1 in |
| LT285/70R17 | 32.7 in |
| LT315/70R17 | 34.4 in |
| 255/60R20 | 32.0 in |
| 255/55R20 | 31.0 in |
| 275/55R20 | 31.9 in |
JK factory sizes, 2007 to 2018
| P225/75R16 | 29.3 in |
|---|---|
| P245/75R16 | 30.5 in |
| P255/75R17 | 32.1 in |
| LT255/75R17 | 32.1 in |
| P255/70R18 | 32.1 in |
TJ and YJ factory sizes
| P205/75R15 | 27.1 in |
|---|---|
| P215/75R15 | 27.7 in |
| P225/75R15 | 28.3 in |
| 30x9.50R15 | 30.0 in |
| LT245/75R16 | 30.5 in |
Common larger sizes
| 31x10.50R15 | 31.0 in |
|---|---|
| 33x12.50R15 | 33.0 in |
| 33x12.50R17 | 33.0 in |
| 285/75R17 | 33.8 in |
| 35x12.50R15 | 35.0 in |
| 35x12.50R17 | 35.0 in |
| 37x12.50R17 | 37.0 in |
| 40x13.50R17 | 40.0 in |
Gearbox table
Wrangler first and top gear ratios
The calculator uses these rows. First gear sets the crawl ratio and top gear sets highway rpm. Every figure is as printed in the Jeep document linked in the last column.
| Gearbox | Fitted to | 1st | Top | Source |
|---|---|---|---|---|
| 8-speed automatic | 2018 to 2026 JL, 4xe and 392 | 4.71 | 0.67 | Jeep 2018 and 2026 specifications |
| 6-speed manual (D478) | 2018 to 2026 JL | 5.13 | 0.72 | Jeep 2018 and 2026 specifications |
| 5-speed automatic (W5A580) | 2012 to 2018 JK | 3.59 | 0.83 | Jeep 2012 to 2018 specifications |
| 6-speed manual (NSG370) | 2012 to 2018 JK | 4.46 | 0.797 | Jeep 2012 to 2018 specifications |
| 6-speed manual (NSG370) | 2007 to 2010 JK | 4.46 | 0.84 | Jeep 2007 to 2010 specifications |
| 4-speed automatic (42RLE) | 2005 TJ, 2007 to 2011 JK | 2.84 | 0.69 | Jeep 2005 to 2011 specifications |
| 5-speed manual (AX15) | YJ and TJ, 4.0L | 3.83 | 0.79 | 1995 and 1999 factory service manuals |
| 5-speed manual (AX5) | YJ and TJ, 2.5L | 3.93 | 0.85 | 1995 and 1999 factory service manuals |
| 3-speed automatic (30RH, 32RH) | TJ | 2.74 | 1.00 | 1999 factory service manual |
How the calculator works
Tire height. For a metric size the height is the wheel diameter plus twice the sidewall, and the sidewall is the width times the aspect ratio. A P245/75R17 is 17 + 2 x (245 x 0.75 / 25.4), which is 31.5 inches. For a flotation size such as 35x12.50R17 the first number is the height.
Speedometer. The Jeep counts wheel turns, so a taller tire covers more ground per turn than the speedometer assumes. True speed is the indicated speed times the new height divided by the old one.
Effective gearing. A taller tire acts like a taller gear. The ratio your axles now behave like is the axle ratio times the old height divided by the new one, and the ratio that brings back the factory feel is the axle ratio times the new height divided by the old one.
Engine rpm. Rpm equals speed in mph times the axle ratio times the top gear ratio times 336, divided by the tire height in inches. The 336 turns miles per hour and inches into revolutions per minute. It assumes a locked torque converter and no clutch slip.
Crawl ratio. First gear times the axle ratio times the transfer case low range. A JL Rubicon with the manual is 5.13 x 4.10 x 4.0, about 84 to 1. Tires do not change the crawl ratio itself, but a taller tire travels farther per engine turn, so the calculator also shows the crawl ratio adjusted for the new tire.
What is not in the list. The gearbox list only has gearboxes whose ratios Jeep printed without contradiction. The TJ manual gearboxes of 2000 to 2006 are missing because the documents for them were not found or disagree with themselves, and Jeep's 2011 sheets give two different sixth gears for the JK manual (0.797 on the two-door sheet, 0.84 on the Unlimited sheet). For those, choose Other and enter the ratios from your own service manual. Jeep's 2005 sheet lists the Rubicon axle as 4.11; use 4.10 here.
Sources
- Stellantis 2026 Jeep Wrangler specifications, and the specification sheets for 2005 and 2007 to 2025, for gearbox, axle and transfer case ratios
- 1999 Wrangler factory service manual and the 1995 Cherokee and Wrangler service manual, for the AX5, AX15 and three-speed automatic
- Our Wrangler bolt pattern guide, for factory tire sizes by year and trim
Last reviewed: November 2026.
Troubleshooting
Owners also ask
Q1 What gear ratio do I need for 35-inch tires on a Jeep Wrangler?
It depends on what you start with. A JL Sport on 3.45 gears and factory 245/75R17 tires (31.5 inches) needs about 3.84 to feel stock on 35s, so the closest factory ratio is 3.73, and 4.10 is the next step down if you want more pull than stock. A JL Rubicon on 4.10 gears and 285/70R17 tires (32.7 inches) needs about 4.39, which makes 4.56 the closest factory ratio.
Q2 How much do bigger tires throw off the speedometer?
By the same percentage as the change in tire height. Going from a 31.5-inch factory tire to a 35-inch tire is an 11 percent increase, so when the speedometer shows 65 mph the Jeep is doing about 72 mph, and the odometer under-counts by the same amount. The error stays until the tire size is reprogrammed in the Jeep's computer.
Q3 Do I need to regear my Jeep for 33-inch tires?
The numbers are modest. On a JL Sport with 3.45 gears, a 33-inch tire is about 5 percent taller than the factory 245/75R17, so the gears act like 3.29 and it would take about 3.62 to match stock. That is a smaller change than the step between two factory ratios. Put your own sizes in the calculator to see your figure.
Q4 How do I work out how tall a tire is from its size?
For a metric size, multiply the width by the aspect ratio to get the sidewall, double it, convert to inches and add the wheel diameter. A 285/70R17 is 285 x 0.70 = 199.5 mm of sidewall, twice that is 399 mm or 15.7 inches, plus 17 inches of wheel: 32.7 inches. For a flotation size such as 35x12.50R17, the first number is already the height in inches.
Q5 What is crawl ratio and how is it calculated?
Crawl ratio is first gear multiplied by the axle ratio and the transfer case's low range. It tells you how many times the engine turns for one turn of the wheels in the lowest gear. A JL Rubicon with the six-speed manual is 5.13 x 4.10 x 4.0, about 84 to 1. With the eight-speed automatic it is 4.71 x 4.10 x 4.0, about 77 to 1.
Q6 What rpm will my Wrangler run at 70 mph?
A JL with the eight-speed automatic, 3.45 gears and factory 31.5-inch tires turns about 1,730 rpm at 70 mph in top gear. Fit 35-inch tires and that drops to about 1,550 rpm. Regearing to 4.10 with the 35s brings it to about 1,850 rpm. The calculator works this out for any Wrangler gearbox on the list.
Q7 Where do I find my Jeep's axle ratio?
Look on the original window sticker, ask a dealer to decode the VIN, or read the metal tag on the differential cover bolts. Jeep's specification sheets list 3.21 as standard on 2012 to 2018 JK Sport and Sahara models, 3.45 on JL Sport and Sahara, and 4.10 on the Rubicon, with 3.73, 4.56 and 4.88 offered on some years and trims.