If you have own old reel to reel tapes, then it’s useful to know how long they’re going to run for. Unfortunately it’s not that straight forward to find out. There are several different speeds that tapes might have been recorded at, and even the diameter of the tape reel isn’t much of a clue. For example there could be anything between 1200 and 2400 feet of tape on a 7 inch reel (this is achieved by the tape itself varying in thickness – 2400 feet on a 7inch reel is pretty thin and much more prone to damage) ,plus of course there are all the different recording speeds to consider as well. The table below gives you a guide as to what tape running times to expect – unfortunately the only way to find out for sure is to play the tape, unless some considerate person had the foresight to label it up!

Reel to Reel Tape Running Times Per Side

Reel Size

Tape Length in Feet
1 7/8 IPS *
3 3/4 IPS *
7 1/2 IPS *
15 IPS *
-
150
16mins
8mins
04mins
2mins
-
200
22mins
11mins
5.4mins
2.7mins
-
225
24mins
12mins
6mins
3mins
-
300
32mins
16mins
8mins
4mins
-
450
48mins
24mins
12mins
6mins
5″
600
1hr 04mins
32mins
16mins
8mins
-
900
1hr 36mins
48mins
24mins
12mins
7″
1200
2hr 08mins
1hr 04mins
32mins
16mins
7″
1800
3hr 12mins
1hr 36mins
48mins
24mins
7″ or 10 1/2″
2400
4hr 16mins
2hr 08mins
1hr 04mins
32mins
10 1/2″
3600
6hr 24mins
3hr 12mins
1hr 36mins
48mins
* IPS=Inches per second – Running Times per Side
CDR
74 minutes
80 minutes
100 minutes
Not sure I would recommend 100 min discs. Not all drives support them and data is very compressed on the disc which can’t be good for accuracy.