Calculadora de Tamanho de Pneu
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
parede = largura × perfil/100; diâmetro = 2×parede + aro×25.4; circunf = π×diâmetro
About this calculator
This tire size calculator determines the outer diameter and circumference of a tire based on the markings on its sidewall, such as 205/55 R16. The calculation uses the tire width in millimeters, the profile height (percentage of width), and the rim diameter in inches. The formula converts the rim to millimeters, calculates the sidewall height, then the total diameter and circumference.
To use the tool, simply enter the width (e.g., 205), the profile (e.g., 55), and the rim diameter (e.g., 16) in the corresponding fields. The calculator applies the formula: sidewall = width × (profile/100); diameter = (2 × sidewall) + (rim × 25.4); circumference = π × diameter. Results are displayed in both millimeters and inches, making it easy to compare with other tires or vehicle specifications.
This calculator is useful in several scenarios: when planning to replace tires with a different size, to check if the new tire maintains correct speedometer calibration, or to calculate distance traveled per revolution. It also helps understand how changes in profile or rim affect overall diameter, which can influence vehicle height, fender clearance, and handling.
Important precautions: always verify that the new tire is compatible with the vehicle, considering clearance, load capacity, and speed rating. Small diameter variations (up to 3%) are usually acceptable, but large changes may affect speedometer accuracy, stability, and ABS function. Consult a professional before altering original specifications.
Frequently asked questions
How do I read tire size markings?
The markings are on the tire sidewall, e.g., 205/55 R16: 205 is width in mm, 55 is profile height as a percentage of width, and 16 is rim diameter in inches.
Can I use a tire with a different diameter than the original?
Yes, as long as the total diameter difference is small (up to 3% higher or lower). Larger differences may affect speedometer accuracy and handling.
What happens if I increase the tire profile?
Increasing the profile raises the sidewall height, increasing total diameter. This may improve comfort but reduces steering precision and may cause fender rubbing.
How does the calculator convert inches to millimeters?
The calculator multiplies the rim diameter in inches by 25.4 to get millimeters, since 1 inch equals 25.4 mm.
Should I worry about tire circumference?
Yes, circumference determines how far the vehicle travels per rotation. Changes affect speedometer reading and recorded distance.