Corrected MPG
Adjusts trip-computer MPG for the odometer error a taller tire introduces.
MPG impact
Correct Tacoma or midsize pickup MPG for tire size.
Enter your indicated MPG and tire sizes to get the corrected figure, plus an annual fuel-cost estimate.
Summary: This calculator corrects a Tacoma or other midsize pickup's trip-computer MPG after a tire size change, since a taller tire makes the odometer under-count miles.
Updated
Is your Tacoma MPG reading wrong with bigger tires?
Yes, if you moved to taller tires and the speedometer was not recalibrated. A taller tire covers more ground per revolution, so the odometer under-counts miles and the displayed MPG reads lower than what the truck really gets. The tables below show how big that error is for common Tacoma stock sizes moving to 31.6-35 inch tires, using the same math as the calculator below. This is the measurement error only. Real fuel use on bigger tires also depends on tire weight, tread, and gearing, which these tables do not estimate; enter your own numbers in the calculator to see both.
How much does each tire size change the MPG reading?
| New tire | Diameter | From 265/70R16 (30.6 in) | From 245/70R17 (30.5 in) | From 265/70R17 (31.6 in) |
|---|---|---|---|---|
| 265/70R17 (~31.6 in) | 31.6 in / 803 mm | +3.27% (×1.033) | +3.61% (×1.036) | 0.00% (×1.000) |
| 275/70R17 (~32.2 in) | 32.2 in / 817 mm | +5.07% (×1.051) | +5.42% (×1.054) | +1.74% (×1.017) |
| 285/70R17 (33s) | 32.7 in / 831 mm | +6.87% (×1.069) | +7.23% (×1.072) | +3.49% (×1.035) |
| 285/75R17 (34s) | 33.8 in / 859 mm | +10.54% (×1.105) | +10.91% (×1.109) | +7.04% (×1.070) |
| 35x12.5R17 (35s) | 35.0 in / 889 mm | +14.36% (×1.144) | +14.74% (×1.147) | +10.74% (×1.107) |
What does a displayed 18.0 mpg really mean?
| New tire | From 265/70R16 (30.6 in) | From 245/70R17 (30.5 in) | From 265/70R17 (31.6 in) |
|---|---|---|---|
| 265/70R17 (~31.6 in) | 18.6 mpg | 18.7 mpg | 18.0 mpg |
| 275/70R17 (~32.2 in) | 18.9 mpg | 19.0 mpg | 18.3 mpg |
| 285/70R17 (33s) | 19.2 mpg | 19.3 mpg | 18.6 mpg |
| 285/75R17 (34s) | 19.9 mpg | 20.0 mpg | 19.3 mpg |
| 35x12.5R17 (35s) | 20.6 mpg | 20.7 mpg | 19.9 mpg |
How do I read these tables?
- Stock sizes in the columns: 265/70R16 (30.6 in / 777 mm), common on 2nd/3rd gen; 245/70R17 (30.5 in / 775 mm), common on 4th gen SR/SR5; 265/70R17 (31.6 in / 803 mm), common on 4th gen TRD Off-Road/PreRunner.
- To correct your own number, multiply the MPG your truck displays by the factor for your stock and new size. The factor is the new diameter divided by the stock diameter.
- Going from 265/70R17 to 285/70R17 without recalibrating, the odometer logs about 96.6 miles for every 100 actually driven, so MPG figured from those miles comes out about 3.4% low.
- Other common stock sizes: 245/75R16 (30.5 in) can use the 265/70R16 column (within 0.1 mpg); 265/65R17 (30.6 in) can use the 265/70R16 column (within 0.1 mpg); 265/65R18 (31.6 in) can use the 265/70R17 column (within 0.1 mpg).
- The math assumes the speedometer was not recalibrated. If a programmer or dealer reflash set the truck to the new tire size, the distance count is already right and no correction applies.
- Diameters come from the size on the sidewall. Real tires vary by brand, tread, load, and wear, so measure or check the maker's spec for a tighter figure.
- This corrects how fuel economy is measured, not how much fuel the truck burns. It also says nothing about whether a size fits; see the max tire size calculator for that.
Plug in your own sizes and MPG with the MPG calculator below. Related: Speedometer correction · Max tire size calculator · Tire size, speedometer, gearing & MPG.
How does this Tacoma MPG and tire size calculator work?
The calculator fixes the fuel-economy number a truck shows you after a tire size change. A Tacoma or any other midsize pickup counts miles by counting tire revolutions, so on a taller tire every revolution covers more road than the computer thinks, and both the odometer and the MPG readout come out low. The calculator undoes that error and, if you give it your miles and fuel price, puts a yearly fuel cost on the corrected figure.
What do I enter?
- Stock tire size: the size the speedometer is calibrated to, usually the one on your door placard.
- New tire size, metric or flotation.
- Indicated MPG: what the trip computer or your fill-up math shows on the new tires.
- Annual miles and price per gallon, used only for the fuel-cost lines.
What does it show?
- Corrected MPG: indicated MPG × new diameter ÷ stock diameter.
- Odometer correction: how far off the distance count is, as a percent.
- Annual fuel cost at the corrected MPG for your miles and fuel price.
- An optional what-if card that subtracts a fixed, hypothetical real-world MPG loss, labeled as an assumption rather than a measurement.
What is the real MPG going from 265/70R17 to 285/70R17 at 18 mpg indicated?
A 2026 TRD Off-Road leaves the factory on 265/70R17 (31.61 in). Put 285/70R17 (32.71 in) on it without recalibrating and the tire is +3.49% taller, so the odometer under-counts by the same share. If the trip computer reads 18 mpg, the truck is really getting 18 × 32.71 ÷ 31.61 = 18.6 mpg.
That correction is measurement only. Whether the truck burns more fuel on the bigger tire depends on its weight, tread, and gearing, which you measure by tracking fill-ups over the corrected miles.
| Truck displays | Really getting on 285/70R17 |
|---|---|
| 15.0 mpg | 15.5 mpg |
| 18.0 mpg | 18.6 mpg |
| 21.0 mpg | 21.7 mpg |
How is it different from a generic calculator?
- Starts from your Tacoma's factory size: the tables above cover the common stock sizes across generations, and each example size links to its Tacoma size page, so the baseline is the tire the truck was calibrated for.
- Separates the measurement error from real fuel use: the correction is a ratio of diameters you can check by hand, and any real-world loss is shown only as a labeled what-if, never folded into the corrected number.
- Recalibration aware: once a programmer or dealer reflash sets the truck to the new size, the readout is already right and no correction applies; the reading notes above say so rather than correcting a number twice.
Do bigger tires really lower a truck's gas mileage?
Partly, and part of what you see is a reading error. On any midsize pickup that has not been recalibrated, a taller tire makes the displayed MPG read low: on 285/70R17 in place of 265/70R17, 18 mpg on the dash is about 18.6 mpg in reality. Any loss beyond that comes from the tire's weight, rolling resistance, and gearing, and the honest way to find it is fill-up math over corrected miles.
Related: 265/70R17 on a Tacoma · 285/70R17 on a Tacoma · Speedometer correction calculator.
What it does
What does this tool do?
Annual fuel cost
Estimates yearly fuel spend and the difference between two fuel-economy figures.
Real efficiency note
Separates the measurement correction from the real 1 to 3 mpg loss bigger tires usually cause.
Which related tools and guides should I use next?
Where do these numbers come from?
A taller tire makes the odometer under-count miles, so true MPG is the displayed MPG times the diameter ratio. That corrects the reading only: it does not estimate how much real fuel economy a heavier or more aggressive tire costs.
- 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
Tire Size MPG Calculator FAQ.
Usually yes by 1 to 3 mpg from added weight and rolling resistance, but the trip computer also under-reports MPG because the odometer under-counts miles. This tool separates the two.
A taller tire travels farther per revolution, so the odometer counts fewer miles than you actually drove. That makes calculated MPG read low until you correct for the diameter change.
Sometimes. On big tires a regear can put the engine back in its efficient range and recover part of the lost fuel economy, though it does not undo the added weight.
Going from 265/70R17 to 35x12.5R17, the odometer under-counts miles by 10.74%, so a displayed 17.0 mpg is really about 18.8 mpg. That is only the measurement error. The heavier, taller tire usually costs a Tacoma or any midsize pickup some real fuel economy as well, which this calculator keeps separate.