How to Estimate Your One-Rep Max Without Testing It
You can estimate your one-rep max (1RM) from a set of a few reps using a simple formula. The most common is the Epley formula: weight lifted × (1 + reps ÷ 30). So 80 kg for 5 reps gives an estimate of about 93 kg. The Brzycki formula, weight × 36 ÷ (37 − reps), gives a similar answer of 90 kg. Both are most accurate with sets of two to six reps taken close to failure but with good form. The result is an estimate, not a fact: use it to set training weights, not to prove anything.
Why estimate instead of test?
Testing a true one-rep max means lifting the heaviest weight you can, once. For competitive lifters peaking for a meet, that has a purpose. For most adults training for strength and health, it has three problems.
- Risk. A maximal single is where form is most likely to slip, especially without experience of lifting near your limit.
- Recovery cost. A real max attempt, with the warm-ups needed to reach it, takes a lot out of you for days.
- Limited payoff. The number on its own does not make you stronger. What matters is choosing good training weights, and an estimate does that almost as well.
So for most people, an estimated max from a hard but controlled set is the better tool.
The formulas
There are many 1RM formulas. Two are widely used and give sensible answers in the useful range.
| Formula | Calculation | 80 kg × 5 reps |
|---|---|---|
| Epley | weight × (1 + reps ÷ 30) | about 93 kg |
| Brzycki | weight × 36 ÷ (37 − reps) | 90 kg |
The two stay within a few kilos of each other up to about ten reps (60 kg for ten gives 80 kg with both). Beyond ten or twelve reps they diverge and both become unreliable, because endurance starts to matter as much as strength. A set of 20 tells you very little about your single best lift.
How to get a reliable estimate
- Warm up properly. A few lighter sets building up to the working weight. Our guide to warming up before lifting keeps this short.
- Pick a weight you can lift three to six times. This range gives the most trustworthy estimates.
- Do one set with good form. Stop when the next rep would be slow or ugly, not when you physically fail. Count only clean reps.
- Use safety bars. For squats and bench presses, set the safeties so a missed rep is harmless.
- Plug the numbers into a formula. Use the same formula every time so results are comparable.
- Record it. Date, lift, weight, reps and estimate. A training log makes the trend visible.
Why estimates are not exact
The formulas assume an average relationship between reps and maximum strength. Real people vary.
- Muscle and training background. Some people can do many reps close to their max; others drop off quickly. Endurance athletes often overestimate; very strength-focused lifters can underestimate.
- The lift. Estimates are usually closer for squats and bench presses than for deadlifts, where grip and fatigue skew the reps.
- Effort. If you stopped with three reps left, the formula will underestimate. If the last rep was a grind with poor form, it will overestimate what you could lift well.
- Day-to-day changes. Sleep, stress and food all shift performance by a few per cent.
Treat the number as a range: within roughly five per cent either way is a reasonable expectation.
Turning the estimate into training weights
Once you have an estimate, you can set loads by percentage. A rough guide that many programmes use:
| Goal | Typical load | Typical reps |
|---|---|---|
| Technique and practice | 50-65% | 5-8, well short of failure |
| Building muscle | 65-80% | 6-12 |
| Building strength | 80-90% | 2-5 |
These are starting points. Many coaches, me included, also use effort-based targets alongside them: finishing a set with one, two or three reps still in reserve. That adjusts automatically for bad days. Reps in reserve and RPE explains how it works.
A worked example
Say your squat set today is 70 kg for five clean reps, stopping with perhaps one more rep possible. Epley gives an estimate of about 82 kg. For a strength block, sets of three to five at 80 to 90 per cent would sit roughly between 65 and 74 kg. For a muscle-building block, sets of eight to ten at 65 to 75 per cent would sit between about 53 and 61 kg. Round to the nearest plate you have, and adjust in the session if the bar moves faster or slower than expected. Six weeks later, if 75 kg goes for five, your estimate has moved to about 88 kg, and the training weights move with it. No max attempt was needed at any point.
How often to re-estimate
Every four to eight weeks is plenty. You do not need a separate test day: a heavy set in your normal training, with clean reps and a known weight, gives you a fresh estimate. If the number rises over months, you are getting stronger. If it stalls, the plan needs changing, not just more effort.
Who should be careful
Even estimation sets involve working hard against a heavy load and often holding your breath. If you have high blood pressure, a heart condition, a hernia, joint injuries, are pregnant, or are returning after a long break, check with your GP first and keep sets further from failure. The NHS strength exercise guidance is a good general reference.
How we use it in the studio
With clients in the basement studio on Archway Road, I rarely test true maxes. We estimate from working sets, set loads from those numbers, and adjust by how each session feels. It keeps training productive and keeps people out of trouble. You can read how coaching works, and see current plans and prices, on the personal training page.
Questions we get asked
Which 1RM formula is most accurate?
No single one is best for everyone. Epley and Brzycki both work well with three to six reps. Choose one and stick with it.
Can I use a set of 10 or more?
You can, but accuracy drops. Above about ten reps, endurance distorts the result.
Do I need to know my 1RM at all?
Not necessarily. Many people train well using reps in reserve alone. An estimate simply helps with planning.
Should beginners estimate their max?
In the first couple of months, there is little point. Technique is still changing too fast for the number to mean much.
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