Bike Tire Size Conversion Calculator

Professional Tire Conversion & Pressure Logic

1. Tire Size

2. Setup

— profile

Status

Enter Data

Rim/Tire compatibility check.

Rec. Pressure

— PSI

Computer

—-

ETRTO

— —

Diameter

—mm

Understanding Bike Tire Sizes

Confused by the numbers on your sidewall? Here is everything you need to know about conversions and fitment.

What is ETRTO / ISO?

This is the only 100% accurate measurement. It looks like 37-622. The first number (37) is the tire width in mm, and the second (622) is the Bead Seat Diameter. If the second number matches your rim, the tire will fit.

Common Name Inches (MTB) ETRTO (ISO)
700c (Road/Gravel) 28" or 29" 622 mm
650b (Gravel/MTB) 27.5" 584 mm
26 Inch (Old MTB) 26" x 1.75-2.2 559 mm
Are 28" and 29" the same?

Yes and no. They both use a 622mm rim. "28-inch" is a European term for road/trekking tires, while "29er" refers to high-volume mountain bike tires. The rim is the same; only the tire thickness changes.

⚠️ Pro Tip: The Decimal vs. Fraction Rule
In the world of 26-inch tires, 26 x 1.75 (decimal) is NOT the same as 26 x 1 ¾ (fraction). They use different rim diameters. Always check the ETRTO number to be safe!
Need to check your internal rim width? Consult your rim manufacturer's specs.