How to Use the Time Under Tension (TUT) Calculator
Lifting the same weight for the same number of reps can produce very different results depending on your tempo. Time under tension (TUT) is the total time your muscle spends under load, and it's a useful way to check whether your training is leaning toward strength, hypertrophy, or endurance. Enter your tempo for each phase — eccentric (lowering), bottom pause, concentric (lifting), and top pause — along with your reps and sets, and this calculator computes your TUT per rep, per set, and for the whole session.
A set-level TUT of 20-40 seconds is widely considered a strong range for hypertrophy (muscle growth). Under 20 seconds usually means heavier weight and a faster tempo, which leans toward strength and power. Over 60 seconds shifts the stimulus toward muscular endurance and metabolic stress, since the muscle spends much longer under continuous load.
Slower tempos make the same weight feel heavier, so it's a good idea to start lighter than usual when trying a new tempo, and to stop immediately if you feel joint pain or excessive shaking.
Frequently Asked Questions
The longer a muscle stays under load, the more metabolic stress and micro-damage it accumulates, which drives hypertrophy. A set-level TUT of 20-40 seconds is generally considered the sweet spot for muscle growth.
Tempo is written as eccentric-bottom pause-concentric-top pause, in seconds. So 3-1-1-0 means 3 seconds lowering the weight, 1 second pause at the bottom, 1 second lifting, and no pause at the top.