Time Under Tension Calculator

About this calculator

Time under tension (TUT) is the total number of seconds a muscle spends actively working during a set, calculated by multiplying each rep’s tempo phases — eccentric (lowering), any pause, concentric (lifting), and any hold — by the number of reps performed. A tempo written as 4-1-2-0, for four seconds down, one second pause, two seconds up, no hold, applied over 10 reps gives 70 seconds of total time under tension.

Bodybuilders and hypertrophy-focused coaches manipulate TUT deliberately because muscle growth responds strongly to how long a muscle stays under mechanical load, not just how much weight moves — slowing the eccentric phase is a common way to increase stimulus without adding weight. Physical therapists use the same concept in the opposite direction, prescribing slow, controlled tempos during rehab to build strength safely under a lighter, more manageable load.