Recovery calculator
DOMS calculator
Say what the session involved and how long ago it was, and see when soreness should peak, when it should be gone, and whether the repeated-bout effect is blunting it. Free, instant, no sign-up.
Soreness is not a training plan. The coach decides what the next few days should hold.
What DOMS actually is
Eccentric contractions — the lowering half of a lift, downhill running, the catch of a drop jump — produce far more soreness than concentric work at the same load, and have done in every study since Armstrong's work in the early 1980s. The mechanism is mechanical damage to the sarcomeres of lengthening muscle, not the lactic acid of gym folklore: lactate is cleared within an hour of finishing and cannot explain soreness that arrives the next day.
The time course is the well-mapped part
Cheung, Hume and Maxwell (Sports Med 2003): soreness develops over the first day, peaks somewhere between 24 and 72 hours, and subsides within five to seven days. Note what that rules out. Soreness an hour after training is not DOMS. Soreness still there at ten days is not DOMS either. Both are worth knowing, and both are what a "how sore will I be" calculator usually gets wrong by treating soreness as a single quantity that decays.
The repeated-bout effect
This is the most robust finding in the literature and the most useful one. A single bout of damaging eccentric exercise confers substantial protection against the same bout performed again — markedly less soreness, less strength loss and smaller rises in creatine kinase the second time round (McHugh, 2003). The protection is specific to the movement rather than to the muscle, and it was still present at six months, reduced at nine and gone by twelve (Nosaka et al., MSSE 2001). It is why the first week back after a layoff is brutal and the second is not, why new eccentric work belongs in a plan in small doses once rather than being avoided, and why the first session back is not a verdict on your fitness. Nosaka's figures come from maximal eccentric elbow flexor work, the standard laboratory insult and harsher than most training, so read them as the outer shape of the effect rather than a schedule.
Why there is no recovery percentage
The magnitude is the badly-mapped part, so this calculator refuses to put a number on it. No published model predicts a soreness score from a description of a session, and any percentage a calculator prints for "recovery" is manufactured. Soreness is measured on subjective scales that do not transfer between people. What survives is an ordering the evidence does support: novel eccentric work hurts most, a repeat of the same eccentric work much less, concentric-only work least. Three ranks is as much resolution as that carries, so three ranks is what you get.
Why the windows do not shrink for an easier session
The peak and resolution windows are the same whatever you enter, and that is a decision rather than an oversight. The repeated-bout effect attenuates how much a bout hurts; the literature does not report it reliably shifting when the peak arrives. Narrowing the window for a familiar session would be inventing a precision nobody has measured. The phase shown here is also a statement about the expected time course, not a reading of how you feel — the calculator is not told that.