Data sheet TS-305/55R20 · Size

305/55R20 in inches

305/55R20 measures 33.2 in (844 mm) overall by the formula. Section width is 12.0 in (305 mm) and sidewall 6.6 in (168 mm).

Fig. 1 — Cross-section

A section width, B sidewall, C rim, D overall diameter. Nominal, on the measuring rim.

Table 1 — Nominal dimensions

305/55R20: nominal dimensions in inches and millimeters
Item	in	mm
Overall diameter	33.21	844
Section width	12.01	305
Sidewall	6.60	167.8
Rim	20	508.0
Circumference	104.3	2,650
Revs per mile · km	607	377

From the makers’ size tables
Flotation size printed	33X12.50R20LT	Mickey Thompson
Measuring rim	9.5″	Nitto LT
Approved rims	9.0–11.0, 8.5–11.0″	15 LT tires

Table 2 — Measured range

33.11–33.70″overall diameter, 20 tires from 5 makers (math: 33.21″)

57–73 lbweight, 15 LT versions

13.5–20.5/32″new tread depth

3,195–3,640 lbmax load per tire, 14 of 15 LT versions list it, as published

15 LT · 5 Pversions in the makers’ tables we read

All 20 tires ↓

Table 3

20 tires in 305/55R20, as published

One row per model and type, from each maker’s size table. LT first, then P-metric; sorted by diameter.

The math says 33.21″. 20 tires from 5 makers measure 33.11″–33.70″. Tallest here: Mickey Thompson Baja Boss A/T (all-terrain), 33.70″. Check the maker’s number before you buy for a tight fit.

Published dimensions for 305/55R20
Tire	Type	Diameter	Width	Rims, in	Weight	Tread	Max load
Nitto Dura Grapplernittotire.com · Oct 15, 2026	LT · E 121/118R	33.11″	12.56″	9.0–11.0	65.6 lb	16.0/32″	3,195 lb @ 65 psi
Firestone Destination X/Tfirestonetire.com · Oct 15, 2026	LT · E 121R	33.20″	—	8.5–11.0	56.8 lb	16.0/32″	—
Kumho Road Venture AT52kumhotireusa.com · Oct 15, 2026	LT · E 121/118S	33.20″	12.40″	9.0–11.0	61.2 lb	16.0/32″	3,195 lb @ 65 psi
Kumho Road Venture RTkumhotireusa.com · Oct 15, 2026	LT · F 125/122R	33.20″	12.40″	9.0–11.0	69.4 lb	17.3/32″	3,640 lb @ 80 psi
Toyo Open Country A/T IIItoyotires.com · Oct 15, 2026	LT · F 125/122Q	33.20″	12.40″	9.0–11.0	65.0 lb	16.8/32″	3,640 lb @ 80 psi
Toyo Open Country R/T Trailtoyotires.com · Oct 15, 2026	LT · F 125/122Q	33.20″	12.40″	9.0–11.0	67.0 lb	16.8/32″	3,640 lb @ 80 psi
Nitto Ridge Grapplernittotire.com · Oct 15, 2026	LT · F 125/122Q	33.23″	12.44″	9.0–11.0	63.9 lb	16.4/32″	3,640 lb @ 80 psi
Nitto Recon Grappler A/Tnittotire.com · Oct 15, 2026	LT · F 125/122S	33.23″	12.44″	9.0–11.0	65.8 lb	16.3/32″	3,640 lb @ 80 psi
Nitto Trail Grappler M/Tnittotire.com · Oct 15, 2026	LT · E 121/118Q	33.39″	12.60″	9.0–11.0	72.1 lb	19.4/32″	3,195 lb @ 65 psi
Mickey Thompson Baja Legend EXPmickeythompsontires.com · Oct 15, 2026	LT · F 125Q	33.40″	12.50″	8.5–11.0	64.0 lb	18.5/32″	3,640 lb @ 80 psi
Kumho Road Venture MT71kumhotireusa.com · Oct 15, 2026	LT · F 125/122Q	33.50″	12.40″	8.5–11.0	73.2 lb	20.0/32″	3,640 lb @ 80 psi
Mickey Thompson Baja Legend MTZmickeythompsontires.com · Oct 15, 2026	LT · F 125Q	33.50″	12.20″	8.5–11.0	68.0 lb	20.5/32″	3,640 lb @ 80 psi
Mickey Thompson Baja Boss M/Tmickeythompsontires.com · Oct 15, 2026	LT · F 125Q	33.50″	12.20″	8.5–11.0	70.0 lb	20.5/32″	3,640 lb @ 80 psi
Toyo Open Country M/Ttoyotires.com · Oct 15, 2026	LT · F 125/122Q	33.50″	12.40″	8.5–11.0	70.0 lb	19.5/32″	3,640 lb @ 80 psi
Mickey Thompson Baja Boss A/Tmickeythompsontires.com · Oct 15, 2026	LT · F 125Q	33.70″	12.20″	8.5–11.0	70.0 lb	18.5/32″	3,640 lb @ 80 psi
Toyo Open Country A/T IIItoyotires.com · Oct 15, 2026	SL 116S	33.20″	12.40″	8.5–11.0	49.0 lb	13.9/32″	2,756 lb @ 44 psi
Toyo Open Country R/T Trailtoyotires.com · Oct 15, 2026	SL 116Q	33.20″	12.40″	8.5–11.0	53.0 lb	13.9/32″	2,756 lb @ 44 psi
Nitto Ridge Grapplernittotire.com · Oct 15, 2026	SL 116Q	33.23″	12.44″	8.5–11.0	51.6 lb	13.5/32″	2,756 lb @ 44 psi
Nitto Recon Grappler A/Tnittotire.com · Oct 15, 2026	SL 116S	33.23″	12.44″	8.5–11.0	51.4 lb	13.9/32″	2,756 lb @ 44 psi
Nitto Terra Grappler G3nittotire.com · Oct 15, 2026	SL 116T	33.23″	12.44″	8.5–11.0	47.6 lb	13.9/32″	2,756 lb @ 44 psi

§ 1

Nominal size numbers

By the formula 305/55R20 has an overall diameter of 33.2 in (844 mm), a section width of 12.0 in (305 mm) and a sidewall height of 6.6 in (168 mm).

Circumference is 104.3 in (2,650 mm). Revolutions per mile are 607 (377 per km). These are unloaded nominal numbers from the size math.

§ 2

What makers publish

Tire makers' size tables list 20 tires in 305/55R20 from 5 brands. The tables show 15 LT versions and 5 P-metric or passenger versions. Load ranges listed include SL, E and F.

Published overall diameters run from 33.11 in to 33.7 in against the 33.21 in nominal (−0.3% to +1.5%). Weights run from 47.6 lbs to 73.2 lbs. New tread depths run from 13.5/32 in to 20.5/32 in.

Nitto Dura Grappler LT305/55R20: 33.11 in diameter, weight 65.6 lbs, tread depth 16/32 in, load range E. (Nitto)
Toyo Open Country A/T III LT305/55R20: 33.2 in diameter, weight 65 lbs, tread depth 16.8/32 in, load range F; Toyo lists 625 revs per mile. (Toyo)
Mickey Thompson Baja Legend EXP LT305/55R20: 33.4 in diameter, weight 64 lbs, tread depth 18.5/32 in, load range F; maker lists equivalent 33X12.50R20LT. (Mickey Thompson)

§ 3

Close sizes and changes

The ±3% overall-diameter window is a tire-shop rule of thumb, not a law. Sizes within that window include 33x11.50R20, 33x12.50R20 and 275/60R20 among others.

Small diameter differences change indicated speed and axle height by small amounts. For example, a 33x11.50R20 is −0.6% (−0.21 in). At an indicated 60 mph the true speed is 59.6 mph and revolutions per mile move from 607 to 611.

33x11.50R20 and 33x12.50R20: −0.6% (−0.21 in); indicated 60 mph → true 59.6 mph; axle height −0.10 in (−3 mm).
275/60R20: −0.7% (−0.22 in); indicated 60 mph → true 59.6 mph; axle height −0.11 in (−3 mm).
Use the comparison tool or the speedometer calculator for other neighbors.

Fig. 2

305/55R20 and the sizes next to it

To scale, on one ground line. Diameter by the formula.

Table 4

Compare 305/55R20 with another size

Type any size: diameter, sidewall, speedometer and clearance change against this one.

Comparison

315/55R20 is 33.64″ tall, +1.30% against 305/55R20. At 60 mph on the dial you drive 60.8 mph.

305/55R20 vs 315/55R20
Item	305/55R20	315/55R20	Change
Overall diameter	33.21″	33.64″	+0.43″ +1.30%
Section width	12.01″	12.40″	+0.39″
Sidewall	6.60″	6.82″	+0.22″
Circumference	104.3″	105.7″	+1.4″
Revs per mile	607	599	−8
Axle height	16.60″	16.82″	+0.22″

When the odometer counts 1,000 miles, you have driven 1,013.0 miles.

Engine RPM at the same road speed: −1.3%. Gear ratio calculator

Speedometer

Speedometer reading and true speed
Dial shows	True speed	Difference
30 mph	30.4 mph	+0.4
45 mph	45.6 mph	+0.6
60 mph	60.8 mph	+0.8
70 mph	70.9 mph	+0.9
80 mph	81.0 mph	+1.0

305/55R20315/55R20

Note 1

P-metric or LT in the same size

Toyo Open Country A/T III is published in both versions.

Toyo Open Country A/T III, 305/55R20: P and LT
Toyo Open Country A/T III	P · 116S	LT · F · 125/122Q
Overall diameter	33.20″	33.20″
Max load	2,756 lb @ 44 psi	3,640 lb @ 80 psi
Weight	49.0 lb	65.0 lb
Tread depth	13.9/32″	16.8/32″
Approved rims	8.5–11.0″	9.0–11.0″

Source: Toyo size table, checked Oct 15, 2026. On trucks and SUVs, the load ratings of the tires on an axle must add up to at least the axle’s GAWR on the certification label (49 CFR 571.110).

Vehicles on 305/55R20: not listed yet. We add a vehicle here only from its maker’s own spec sheet for that year and trim.

The size your vehicle left the factory on is printed on the tire and loading placard on the driver’s door jamb (49 CFR 571.110). Pressure and load: that placard too.

Table 5

Within 3% of 305/55R20

Same rim or ±1″, diameter within 3%. A shop rule of thumb, not a law.

Sizes within 3% of 305/55R20
Size	Diameter	Width	vs 305/55R20	At 60 mph	Clearance
33x11.50R20	33.00″	11.5″	−0.6%	59.6	−0.10″
33x12.50R20	33.00″	12.5″	−0.6%	59.6	−0.10″
275/60R20	32.99″	10.8″	−0.7%	59.6	−0.11″
285/60R20	33.46″	11.2″	+0.8%	60.5	+0.13″
295/55R20	32.78″	11.6″	−1.3%	59.2	−0.22″
265/60R20	32.52″	10.4″	−2.1%	58.8	−0.34″
295/60R20	33.94″	11.6″	+2.2%	61.3	+0.36″
34x11.50R20	34.00″	11.5″	+2.4%	61.4	+0.40″
275/65R20	34.07″	10.8″	+2.6%	61.6	+0.43″
285/55R20	32.34″	11.2″	−2.6%	58.4	−0.43″

Other 20″ sizes

Q&A

Common questions

How many revolutions per mile does 305/55R20 make?

By the formula 305/55R20 makes 607 revs per mile (377 per km).

Do makers publish different diameters for 305/55R20?

Yes. Makers' tables list diameters from 33.11 in to 33.7 in, which is −0.3% to +1.5% versus the nominal 33.21 in.

What load ranges are available for 305/55R20?

Manufacturer size tables for 305/55R20 show load ranges SL, E and F. The sidewall shows the maximum load rating and, for LT tires, the load range letter per 49 CFR 571.139 (FMVSS No. 139).

Where is the vehicle inflation and load info?

See the tire and loading placard on the driver's door jamb for the vehicle maker’s recommended cold pressures and load ratings as required by 49 CFR 571.110 (FMVSS No. 110).

Notes

Method and sources

Each number and rule comes from a source with the date it was checked.

Sidewall = width × aspect ratio ÷ 100
Diameter = rim × 25.4 + 2 × sidewall (mm)
Revs per mile = 63,360 ÷ (π × diameter, in)
True speed = dial × new diameter ÷ old diameter
Clearance change = half the diameter change

Numbers are nominal: the tire unloaded, on its measuring rim. Revs per mile published by makers run higher than the formula. “Within 3%” is a rule of thumb tire shops use, not a law. Tire pressure: the placard on your door jamb.

Nitto: size table (nittotire.com)checked Oct 15, 2026
Toyo: size table (toyotires.com)checked Oct 15, 2026
Mickey Thompson: size table (mickeythompsontires.com)checked Oct 15, 2026
49 CFR 571.139 (FMVSS No. 139), S5.5(d)ecfr.gov · checked Oct 15, 2026
49 CFR 571.110 (FMVSS No. 110), S4.3ecfr.gov · checked Oct 15, 2026

Calculators and size classes

33″22 metric and 11 flotation sizes measure 32.5–33.5″ by the formula305/70R16 · 285/75R16 · 295/75R16 · 305/65R17 · 285/70R17 35″15 metric and 16 flotation sizes measure 34.5–35.5″ by the formula315/75R16 · 325/65R18 · 305/70R18 · 285/75R18 · 285/65R20 37″3 metric and 13 flotation sizes measure 36.5–37.5″ by the formula385/70R16 · 315/80R17 · 375/45R24