Time Under Tension Calculator
Add up how long your muscles are working under load, per set and across the session.
Fill in the form and your result lands here.
Learn the details
Time Under Tension (TUT) is reps × tempo, the total seconds a muscle spends under load in a set. The 40 to 70 second range shown for hypertrophy is a common programming convention, not a growth requirement: hard sets taken near failure drive growth across a much wider range of tempos.
The math here is simple, tempo times reps. The part worth arguing about is what those seconds actually buy you, so here is the honest version, including how much weight that famous 40 to 70 second window deserves.
What this adds up
A rep gets split into four phases: the eccentric, which is the lowering, a pause at the bottom, the concentric, which is the lift, and a pause at the top. The calculator sums the seconds you enter for those four to get one rep, multiplies by your reps to get a set, then multiplies by your sets to get the session total. Any phase you leave blank counts as zero, and you need at least one filled in. Notice what is not in the math: no load, no rest between sets, no measure of how hard the set was. This is a stopwatch, not a training prescription.
A worked example
Say you lower for 3 seconds, pause 1 second at the bottom, lift for 2 seconds, and take no pause at the top. That is 6 seconds per rep. Ten reps puts a set at 60 seconds, and four of those sets gives 240 seconds, which the tool shows as 4m. Against the ranges table, 60 seconds reads In Range for hypertrophy, 20s above for strength, and 10s below for endurance. Now try a 4 second lowering with a 1 second lift, so 5 seconds per rep, 8 reps, 3 sets. That is 40 seconds per set and 2m total, and the table calls it In Range for strength and hypertrophy at the same time, because the bands touch at 40. That overlap is a good reminder of how rough these bands are.
About that 40 to 70 second window
The ranges table on this page repeats the standard claim, and I want to be straight with you: it is a programming convention, not a requirement for growth. The way I would frame it is that size follows the number of hard sets you do and how near failure you take them, far more than the seconds a rep happens to last. Deliberately grinding a rep out slowly also cuts the load you can handle and the reps you can complete, so your seconds go up while the hard work goes down. Read your number as a description of the tempo you used, not a target to chase.
What tempo is genuinely good for
Controlling tempo is still worth doing, just for different reasons than the folklore says. It is one of the best ways to learn a new movement, because a slow lowering forces you to own every inch of the range instead of dropping into it. It kills the bounce, so a paused squat or bench rep is an honest rep. It makes a light load feel meaningful when your equipment is limited, which is the whole trick behind home and hotel workouts. And it is a way to keep training hard on days when joints would rather not see a heavy bar. For most people, one to two seconds of real control on the way down is plenty.
What to track instead
Use this number to check that your tempo is what you think it is, then go track the things that change your results. How much you lift and how often you beat it belongs in progressive overload, total work per session belongs in volume load, and if you are unsure how many reps to aim for in the first place, the rep range guide is the better starting point. Tempo is a control you apply on purpose, not the mechanism behind your results.
Focus on the eccentric: a 3-4 second lowering with a 1 second concentric is a good start, without sacrificing much load. Most useful in hypertrophy phases or when joints need a break from heavy weights.