How to distinguish whether the threaded rod is ASTM (British) or German din975 (metric)

1. Look at the thread specification marking to distinguish whether the threaded rod is ASTM (British) or German DIN (metric)

American (British) ASTM threaded rod
➤ Expressed in inches, such as:
1/4″-20 (diameter 1/4 inch, 20 threads per inch)
3/8″-16 (diameter 3/8 inch, 16 threads per inch)
➤ The marking may be UNC (coarse thread) or UNF (fine thread).

German (metric) DIN975
➤ Expressed in millimeters, such as:
M6×1.0 (diameter 6mm, pitch 1.0mm)
M8×1.25 (diameter 8mm, pitch 1.25mm)
➤ The marking may be DIN or ISO standard number (such as DIN975).

 2. Measure the thread diameter to distinguish whether the stud bolt is threaded rod is ASTM (British) or German DIN (metric)

Use a caliper to measure the external thread diameter:

The value is an integer or a common fraction (such as 1/4″, 5/16″) → American ASTM threaded rod

The value is a whole number of millimeters (such as 6mm, 8mm) → German

3. Measure the pitch (key difference) to distinguish whether the  threaded rod is ASTM (British) or German DIN (metric)

American: count the number of  threaded rod per inch (such as 20 teeth/inch ≈ 1.27mm pitch).

German: directly measure the millimeter distance between the two tooth tips (such as 1.0mm, 1.5mm).
Use a pitch gauge or ruler to compare and distinguish!

4. Look at the thread angle to distinguish whether the threaded rod is ASTM (British) or German DIN (metric)

American: angle 60° (UN/UNF standard).

German: 60° thread angle (metric standard), but the German standard may pay more attention to surface treatment (such as anti-rust coating).
(Note: The angle needs to be measured with professional tools, and the specifications and pitch can be prioritized in daily life.)