The comparison for isometrics that I used in Overcoming Gravity is 1 repetition = 2s isometric hold. Once you know the approximate repetitions, you can plug into a 1 RM calculator
This gives a pretty solid comparison, and it's based off a lot of my experience and coaching gymnastics/parkour for stuff like back lever, front lever, planche, iron cross, etc.
A couple use notes:
2"RM is the maximal weight you can hang for 2 seconds, just like 1RM is the maximal weight with which you can do 1 rep.
If you are doing no-hangs, just use the weight itself; if you're doing normal hangs, make sure to include bodyweight (total weight= bodyweight + weight added).
Sometimes these equations will spit out answers that don't really make sense, e.g. negative hang times. Checking 'sensible outputs' mitigates that as follows:
no negative hang times; outputs 0 instead.
unfortunately some of the formulas will still output ludicrous hang times with submaximal weight.
when calculating hang times:
if the weight is more than your 2"RM, output 0 seconds.
if the weight is your 2"RM, output 2".
when calculating 2"RM: if you hang 2" with a weight, output that entered weight.
What is my 2"RM if I hang
total weight
for
seconds?
Average
Epley
Brzycki
McGlothin
Lombardi
Mayhew
O'Conner
Wathen
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-
-
-
-
-
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If my 2"RM is
how long can I hang
?
Average
Epley
Brzycki
McGlothin
Lombardi
Mayhew
O'Conner
Wathen
-
-
-
-
-
-
-
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If my 2"RM is
how much weight can I hang for
seconds?
Average
Epley
Brzycki
McGlothin
Lombardi
Mayhew
O'Conner
Wathen
-
-
-
-
-
-
-
-
If I can hang weight for seconds, how long can I hang ?
Average
Epley
Brzycki
McGlothin
Lombardi
Mayhew
O'Conner
Wathen
-
-
-
-
-
-
-
-
If I can hang weight for seconds, how much weight can I hang for seconds?
Average
Epley
Brzycki
McGlothin
Lombardi
Mayhew
O'Conner
Wathen
-
-
-
-
-
-
-
-
Equations
Note: t is hang time in seconds, m is 2"RM, and w is total weight.