How long to hold a plank, in short: 20 to 30 seconds if you are starting, 60 seconds as a target worth working towards, and two minutes as a genuinely strong hold. Past two minutes you are mostly training patience, and there are better uses of the next three minutes.

The rough benchmarks

Level	Hold	What it looks like
Starting out	20-30s	Form holds the whole way, no sag at the end
Building	45s	Last 10 seconds are work but not a fight
Solid	60s	The standard target, and enough for most purposes
Strong	2 min	Uncommon with genuinely good position throughout
Diminishing returns	Past 2 min	Endurance of the position, not much new strength

These are hold-with-good-form numbers, which is the only kind worth counting. A three-minute plank with your hips dropped and your lower back arched is three minutes of practising a bad position under load.

The form check that decides the number

Before the clock matters, the position does:

Elbows under shoulders, forearms flat.
Ribs pulled down, not flared. Think of shortening the distance between the bottom of your sternum and your pubic bone.
Glutes on. This is the cue most people are missing and it changes the hold completely.
Neutral neck, eyes at the floor a little ahead of your hands.
Breathing. If you are holding your breath, the hold has already failed.

The moment the low back starts to arch or the hips drop, the set is over. Not “over in ten more seconds”.

Why longer is not better

Stuart McGill, the spine biomechanist at the University of Waterloo, is the name most associated with the argument against very long holds. His general position across his work on spine stability is that endurance in the trunk musculature matters more than maximal strength, but that endurance is best built with repeated shorter holds rather than a single long one, because form and muscle activation degrade as the hold extends and you end up training the compensation rather than the pattern. The practical recommendation associated with his work is holds of roughly ten seconds, repeated, with brief rests, rather than one hold to failure.

That is a paraphrase of the reasoning, not a quotation, and it is worth reading his own material if you want the specifics. The takeaway is uncontroversial regardless of whose name is on it: ten quality ten-second holds are a better stimulus than one shaky ninety-second one.

He is also the source of the RKC plank, a much harder version of the same position: elbows pulled towards your toes, glutes and quads maximally contracted, everything braced as hard as you can. Held properly it is very difficult to sustain for more than ten or fifteen seconds, which tells you something about what a comfortable two-minute plank is actually measuring.

Progressions that beat adding time

Once 60 seconds is comfortable, add difficulty rather than duration.

Progression	How	Target
RKC plank	Maximal full-body tension, shortened lever	10-15s
Side plank	One forearm, hips stacked, top arm up	30-45s a side
Long-lever plank	Elbows further forward of the shoulders	20-30s
Shoulder taps	Tap opposite shoulder, resist the hip rotation	10 a side
Weighted plank	A plate on the upper back, someone to place it	30-45s
Feet elevated	Toes on a bench	30s

Side planks deserve particular attention because they train the lateral trunk, which a front plank largely does not, and most people are noticeably worse on one side. Do the weak side first and match the strong side to it.

Running plank intervals

Repeated short holds need a timer that beeps twice, not once, and the plank timer handles the single hold. For the interval version, build it on interval:

McGill-style endurance set: work 10s, rest 5s, 8 rounds. Two minutes total, eight quality holds.

Standard set: work 30s, rest 30s, 6 rounds. Six minutes.

Front and side circuit: work 30s, rest 15s, 6 rounds, alternating front, left side, right side, twice through.

Set rest to 0 and you get one continuous hold with a beep at each boundary, which is a way to break a long hold into countable chunks without stopping. For a plain single hold, 60 seconds and 2 minutes are there too, and the plank timer keeps the screen on so it does not go dark on the floor beside you.

A realistic weekly dose

Two or three sessions a week, three to five sets, mixing a front variation with a side variation. Total time under tension per session of somewhere between one and three minutes is plenty. If you have five minutes for core work, spending all of it on one long front plank is the least productive way to use it.

Try it: hold a plank on the plank timer.