How Many Sit-Ups Should I Do Per Day?
Here's the answer most pages won't give you: fewer than you'd expect — possibly none. If sit-ups make your lower back feel strained, that's not you doing them wrong. It's the exercise. There are gentler, more effective ways to build a strong core, and this page helps you find them.
Sit-up swap finder
What matters most to you? The list re-sorts to match.
Your lower back stays flat on the floor the whole time — about as spine-friendly as core work gets.
Anti-rotation, no flexion — one of physiotherapist Stuart McGill’s recommended “big three”.
An isometric hold with a neutral spine — the exercise militaries adopted to replace the sit-up.
Trains the sides of your core without bending the spine at all.
A much smaller range than a sit-up; the lower back stays pressed down, easing the strain.
Curls the hips up toward the chest, with far less load on the lower back than a full sit-up.
Tougher — effective, but only once you can keep your lower back pressed flat.
Full spinal flexion plus heavy hip-flexor pull — the very pattern that tends to nag the lower back.
General starting ranges, not a prescription. Build up gradually, and if a movement causes pain (not just effort), stop and check with a professional.
Notice where the sit-up lands once you sort by what's kindest to your spine — bottom of the list. That's the whole point.
The honest answer
If you do want a number: a reasonable starting point is a couple of sets of 10 to 15 controlled repetitions, a few days a week — not every day, since the core needs recovery like any other muscle. But the volume barely matters compared to the bigger question, which is whether the sit-up is the right tool at all.
Quality always beats quantity here. Thirty slow, controlled reps with the core genuinely engaged do far more than a hundred fast ones thrown up with momentum and hip flexors. And if the movement consistently strains your back, the smartest "rep count" is zero — swapped for something that builds the same strength without the cost.
Why sit-ups nag your back
The strain you feel has a clear mechanical cause. A full sit-up repeatedly bends your spine forward under load — spinal flexion — and the spine biomechanist Stuart McGill's research showed that doing this over and over raises the risk of lower-back and disc injury. On top of that, once your feet are anchored, much of the lift comes from the hip flexors rather than the abs. Tight, overworked hip flexors tug the lower spine into an arch, which is exactly where that achy, strained feeling comes from.
This isn't a fringe opinion any more. The US Army replaced the sit-up with the plank in its fitness test, the Navy and Marines moved to a forearm plank, and the Canadian and Australian forces dropped sit-ups too — all citing back safety and the fact that real-world strength is about stability, not curling up off the floor. Your instinct to avoid them puts you in good company.
What to do instead
The exercises in the finder above all train the core through stability rather than repeated bending — which is both safer for the spine and closer to what your core actually does in daily life: bracing, resisting, holding you steady.
A gentle, evidence-based place to start is what McGill calls the “big three”: the bird dog, the side plank, and a short, shallow curl-up. Add the dead bug (lower back glued to the floor) and a standard forearm plank, and you've got a full core routine that hits the deep stabilising muscles — the transverse abdominis especially — without a single full sit-up. If you like the feel of a crunch, a small-range crunch or reverse crunch keeps the lower back far happier than the full movement.
“To get abs” — the real story
A lot of sit-up searches are really asking how to get visible abs, so it's worth being straight about it: you can't spot-reduce fat. No amount of sit-ups burns fat specifically from your stomach. Core exercises build and strengthen the muscle underneath, but whether it shows is governed by your overall body-fat level, which comes down to your general eating and activity habits, not crunches.
So the honest path to a stronger, more visible core is sustainable, whole-body habits plus a bit of varied core work — not grinding out daily sit-ups. Treat core training as building strength and stability that protects your back, and let appearance follow from a healthy overall routine rather than chasing it directly.
Calories burned (not many)
Sit-ups are a poor calorie-burner because they work small muscles in short bursts — roughly 3 to 6 calories a minute depending on your size and pace. That's why "how many sit-ups burn 100 calories" has such a deflating answer: you'd be at it for twenty to thirty minutes, doing hundreds of reps.
To burn just 100 calories you'd need around 21 minutes of continuous sit-ups — roughly a small banana's worth. A brisk walk does it faster and far more comfortably.
The takeaway: sit-ups aren't a weight-loss tool. For burning energy, walking, cycling or any continuous activity is far more efficient — and far kinder to your spine.
Listening to your back is good training
The question "how many sit-ups should I do" quietly assumes sit-ups are the goal. They aren't — a strong, stable, pain-free core is. Once that's the target, the sit-up is just one option among many, and not a particularly good one for most people.
Disliking an exercise that strains your back isn't a lack of discipline; it's useful feedback. The best routine is the one you'll keep doing without getting hurt — so swap the sit-up out and keep going.
Common questions
Sources & notes
- Spinal-flexion injury risk and the “big three” core exercises — Stuart McGill, spine biomechanics (University of Waterloo).
- Militaries replacing sit-ups with the plank — US Army ACFT; US Navy and Marine Corps forearm plank; Canadian and Australian forces.
- Calorie estimates — MET-based: moderate sit-ups ≈ 3–6 kcal/min; neither sit-ups nor planks burn significant calories.
- Spot reduction of fat is not possible; visible abs depend on overall body composition.
- This is general information, not medical or training advice. Build up gradually, and see a qualified professional for persistent back pain or before starting a new routine.
More on training & the body
The best number of sit-ups might be none — your back already knew that.