How to measure 8 & 16 mm film:

AVRestore - Film Reel Measurements

1. Measure the reel across as shown in the picture above.
2 . Get the film length from the table below:

Diameter (inches)
Film length (ft)
2-7/8"
50 ft.
3-5/8"
100 ft.
5"
200 ft.
7"
400 ft.
9-1/4"
600 ft
10-1/2"
800 ft.
12-1/4"
1,200 ft.
13-11/16"
1,600 ft
15"
2,000 ft.
15" with small hub
2,300 ft.