Tyre Size Calculator
Overall diameter, rolling circumference and sidewall height from a tyre code.
Results
Diameter
631.9
mm
Circumference
1.9852
m
Height
112.8
mm
Quantity
503.7
/km
What this tool does
A code like 205/55 R16 mixes millimetres, a percentage and inches in one string. The aspect ratio is the sidewall height as a percentage of the width, which is why a wider tyre with the same profile number is also taller.
Formula
diameter = rim × 25.4 + 2 × width × profile ÷ 100
Variables
| Symbol | Meaning | Unit |
|---|---|---|
w | Tyre width | mm |
a | Aspect ratio | % |
r | Rim diameter | in |
D | Diameter | mm |
C | Circumference | m |
SW | Height | mm |
RK | Quantity | /km |
Worked example
- Tyre width205 mm
- Aspect ratio55 %
- Rim diameter16 in
- Diameter631.9 mm
- Circumference1.9852 m
- Height112.8 mm
- Quantity503.7 /km
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.