What should I verify before using this information?

Use TireFitLab values as a sizing reference, then verify the vehicle handbook, tire placard, rim compatibility, load rating, and physical clearance before fitting.

How to read a tire size

What does P205/55R16 91V mean?

P = passenger vehicle (optional). 205 = section width in mm. 55 = aspect ratio (sidewall = 55% of width). R = radial construction. 16 = rim diameter in inches. 91 = load index (615 kg per tire). V = speed rating (up to 240 km/h). XL = extra load; RF = run-flat (optional suffixes).

P = passenger vehicle (optional).
205 = section width in mm.
55 = aspect ratio (sidewall = 55% of width).

FAQ

What does P205/55R16 91V mean?: P = passenger vehicle (optional). 205 = section width in mm. 55 = aspect ratio (sidewall = 55% of width). R = radial construction. 16 = rim diameter in inches. 91 = load index (615 kg per tire). V = speed rating (up to 240 km/h). XL = extra load; RF = run-flat (optional suffixes).
What should I verify before using this information?: Use TireFitLab values as a sizing reference, then verify the vehicle handbook, tire placard, rim compatibility, load rating, and physical clearance before fitting.

How-to steps

Find the size string Read the full sidewall marking from left to right, including service prefix, width, aspect ratio, construction, rim diameter, load index, and speed symbol.
Decode the metric fields Convert width, aspect ratio, and rim diameter into sidewall height and overall diameter before comparing it with another size.
Check service description Confirm load index and speed symbol meet or exceed the vehicle requirement before fitting.

Decode a tyre size

Type the main sidewall size string to see the width, profile and sidewall math.

Tyre size

Section width: 225 mm
Aspect ratio: 45%
Sidewall height: 101.3 mm
Overall diameter: 634.3 mm

Reference-table value only. Always match your vehicle placard and tire sidewall markings.

Worked examples

Metric and flotation markings look different, but the table is calculated from the same nominal diameter, width and rim-size rules.

Size	Overall diameter	Section width	Sidewall	Circumference
225/45R17	24.97 in / 634 mm	8.86 in / 225 mm	3.99 in / 101.3 mm	78.45 in / 1993 mm
285/75R16	32.83 in / 834 mm	11.22 in / 285 mm	8.42 in / 213.8 mm	103.14 in / 2620 mm
33x12.50R15	33.00 in / 838 mm	12.50 in / 318 mm	9.00 in / 228.6 mm	103.67 in / 2633 mm

What to do with it: Round marketing sizes can hide several millimetres of difference.

P205/55R16 91V — field by field

Field	Example	Spec
P	`P205/55R16 91V`	Vehicle type prefix. P = passenger. LT = light truck. No prefix = Euro-metric. Optional — most EU tires omit it.
205	`P205/55R16 91V`	Section width in millimetres. The widest point of the tire when properly inflated and mounted on the specified rim.
55	`P205/55R16 91V`	Aspect ratio — sidewall height as a percentage of the section width. A 205mm wide tire with a 55 ratio has a 112.75mm tall sidewall (205 × 0.55).
R	`P205/55R16 91V`	Construction type. R = radial (standard on all modern passenger tires). D = diagonal/bias-ply (rare; trailers, some off-road). B = bias-belted.
16	`P205/55R16 91V`	Rim (wheel) diameter in inches. The tire must match the rim diameter exactly.
91	`P205/55R16 91V`	Load index — the maximum load capacity per tire. 91 = 615 kg. Used in pairs: for a 1,500 kg axle load you need 2 × 750 kg, so LI ≥ 97.
V	`P205/55R16 91V`	Speed rating — the maximum sustained speed. V = 240 km/h. Common ratings: T=190, H=210, V=240, W=270, Y=300 km/h.
XL or RF (optional)	`P205/55R16 91V XL`	XL (Extra Load) or reinforced — higher maximum inflation pressure and load capacity. RF or RFT = run-flat — can be driven 80 km at 80 km/h after puncture.

Tire size calculator · Tire type guide — P, LT, metric, radial & flotation · Tire load index chart · Tire speed rating chart · Tire & wheel reference guides

Last reviewed: 2026-06-28

What changed

Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.