True speed
Shows actual speed for any indicated speed, since a taller tire travels farther per revolution.
Speedometer correction
Check your Tacoma or midsize pickup speedometer error.
Compare your stock and new tire size to see how far off the speedometer reads and your true speed at any indicated speed.
Summary: This calculator shows how far off a Tacoma or other midsize pickup's speedometer reads after a tire size change, and your true speed at any indicated speed.
Updated
How far off is a Tacoma speedometer with bigger tires?
A taller tire makes a Tacoma's speedometer read low: the truck covers more ground per wheel revolution than the factory calibration assumes, so true speed is higher than the number shown and the odometer under-counts miles. This table lists true speed when the speedometer shows 60 and 70 mph, and true miles per 10,000 on the odometer, for common stock sizes and popular 31.6-35 inch upsizes. It uses the same diameter math as the calculator below.
| Stock → upgrade | Stock fitment | Diameter | Change | True speed, reads 60 | True speed, reads 70 | True miles per 10,000 odometer |
|---|---|---|---|---|---|---|
| 265/70R16 → 265/70R17 | Common 2nd/3rd gen off-road OEM size | 30.61 → 31.61 in (777 → 803 mm) | +3.27% | 62.0 mph | 72.3 mph | 10,327 mi (+327) |
| 265/70R16 → 275/70R17 | Common 2nd/3rd gen off-road OEM size | 30.61 → 32.16 in (777 → 817 mm) | +5.07% | 63.0 mph | 73.5 mph | 10,507 mi (+507) |
| 265/70R16 → 285/70R17 | Common 2nd/3rd gen off-road OEM size | 30.61 → 32.71 in (777 → 831 mm) | +6.87% | 64.1 mph | 74.8 mph | 10,687 mi (+687) |
| 265/70R16 → 285/75R17 | Common 2nd/3rd gen off-road OEM size | 30.61 → 33.83 in (777 → 859 mm) | +10.54% | 66.3 mph | 77.4 mph | 11,054 mi (+1,054) |
| 265/70R16 → 35x12.5R17 | Common 2nd/3rd gen off-road OEM size | 30.61 → 35.00 in (777 → 889 mm) | +14.36% | 68.6 mph | 80.0 mph | 11,436 mi (+1,436) |
| 245/70R17 → 265/70R17 | Common 4th gen SR/SR5 OEM size | 30.50 → 31.61 in (775 → 803 mm) | +3.61% | 62.2 mph | 72.5 mph | 10,361 mi (+361) |
| 245/70R17 → 275/70R17 | Common 4th gen SR/SR5 OEM size | 30.50 → 32.16 in (775 → 817 mm) | +5.42% | 63.3 mph | 73.8 mph | 10,542 mi (+542) |
| 245/70R17 → 285/70R17 | Common 4th gen SR/SR5 OEM size | 30.50 → 32.71 in (775 → 831 mm) | +7.23% | 64.3 mph | 75.1 mph | 10,723 mi (+723) |
| 245/70R17 → 285/75R17 | Common 4th gen SR/SR5 OEM size | 30.50 → 33.83 in (775 → 859 mm) | +10.91% | 66.5 mph | 77.6 mph | 11,091 mi (+1,091) |
| 245/70R17 → 35x12.5R17 | Common 4th gen SR/SR5 OEM size | 30.50 → 35.00 in (775 → 889 mm) | +14.74% | 68.8 mph | 80.3 mph | 11,474 mi (+1,474) |
| 265/70R17 → 275/70R17 | Common 4th gen TRD PreRunner/TRD Off-Road size | 31.61 → 32.16 in (803 → 817 mm) | +1.74% | 61.0 mph | 71.2 mph | 10,174 mi (+174) |
| 265/70R17 → 285/70R17 | Common 4th gen TRD PreRunner/TRD Off-Road size | 31.61 → 32.71 in (803 → 831 mm) | +3.49% | 62.1 mph | 72.4 mph | 10,349 mi (+349) |
| 265/70R17 → 285/75R17 | Common 4th gen TRD PreRunner/TRD Off-Road size | 31.61 → 33.83 in (803 → 859 mm) | +7.04% | 64.2 mph | 74.9 mph | 10,704 mi (+704) |
| 265/70R17 → 35x12.5R17 | Common 4th gen TRD PreRunner/TRD Off-Road size | 31.61 → 35.00 in (803 → 889 mm) | +10.74% | 66.4 mph | 77.5 mph | 11,074 mi (+1,074) |
How do I read this table?
- Read the speed columns as: the speedometer reads 60 (or 70) mph, and the truck is actually doing the listed speed. Change is the overall diameter change, which equals the speedometer and odometer error.
- Diameters are nominal, calculated from the size printed on the sidewall. Real tires run a little shorter or taller by brand, tread depth, and pressure, so a GPS check is the final word.
- Speedometer error depends only on overall diameter. A regear does not fix it, because the speed sensor reads at the wheel hub; recalibration with a tuner or dealer tool does.
- This is speed and distance math, not a fitment rating. Many of these sizes need a level, a lift, or trimming on a given generation; check the max tire size calculator before you buy.
How does this speedometer calculator work?
The calculator compares the tire size your speedometer was calibrated for with the size on the truck now. It works out each tire's overall diameter from the sidewall numbers (wheel diameter plus two sidewall heights, where sidewall height is section width times aspect ratio, converted to inches), then divides the new diameter by the stock one. That single ratio drives every result.
You enter the stock size, the new size, and the speed the speedometer shows. It returns the diameter change, the speedometer error in percent, your true speed at that reading, and a short indicated-versus-true speed table. Odometer error is the same percentage as the speedometer error; the table above converts it to miles.
Worked example, 265/70R17 → 285/70R17 (the pair the calculator opens on): the speedometer reads 3.49% low, so an indicated 60 mph is really 62.1 mph and an indicated 70 mph is really 72.4 mph.
It differs from a generic tire calculator in two ways. It starts from Tacoma factory sizes, from the 4th-gen TRD default to the common stock sizes for each generation in the table above, and the tire size guide lists the stock size for each year and trim. And it shows its math, so you can check every step; figures are rounded for display, while the calculator carries full precision.
| Step | 265/70R17 → 285/70R17 |
|---|---|
| Stock diameter (265/70R17) | 17 + 2 × 7.30 = 31.61 in |
| New diameter (285/70R17) | 17 + 2 × 7.85 = 32.71 in |
| Diameter change = speedometer error | 32.71 ÷ 31.61 ≈ 1.0349 (+3.49%) |
| True speed when it reads 60 mph | 60 × 1.0349 ≈ 62.1 mph |
| True speed when it reads 70 mph | 70 × 1.0349 ≈ 72.4 mph |
| True miles per 10,000 on the odometer | 10,000 × 1.0349 ≈ 10,349 mi |
To recalibrate or check another size, enter your stock and new size in the Speedometer Correction Calculator below. Related: Max tire size calculator · Gear ratio calculator · Stock tire size by year and trim · Tire size, speedometer, gearing & MPG.
What it does
What does this tool do?
Percent error
Reports the speedometer error and flags whether it is inside the roughly 3 percent safe window.
Gearing note
Explains that a regear does not change speedometer error; only tire diameter does.
Which related tools and guides should I use next?
Where do these numbers come from?
Speedometer error is the ratio of the new tire's diameter to the stock tire's, so the math itself needs no outside source. What needs checking is your starting point, which is why the stock size should come from your placard or Toyota's manual.
- Tire geometry: computed from the numbers in each size code with this site's published formulas (no outside data)
- Toyota 2026 Tacoma Owner's Manual tire and wheel specs: factory tire sizes and wheel widths
Speedometer Correction Calculator FAQ.
Bigger tires make the speedometer read low. The truck travels farther per wheel revolution than the factory calibration assumes, so your actual speed is higher than the number shown.
Within about 3 percent is considered excellent and usually not worth correcting. Beyond about 5 percent is where most owners recalibrate for accuracy and to keep the odometer honest.
No. The Tacoma speed sensor reads at the wheel hub, so tire diameter causes the error and axle gears do not change it. Recalibrate with a tuner or dealer tool instead.
It depends on the size you start from. On a Tacoma moving from 265/70R17 to a 285/70R17, the speedometer reads 3.49% low: an indicated 65 mph is really 67.3 mph, and every 1,000 miles on the odometer is about 1,035 miles driven. Any midsize pickup works the same way, because the error is just the change in overall diameter.