Free tool
One Rep Max Calculator
Your one rep max (1RM) is the heaviest weight you could lift once. Type the weight and reps from one hard set. You get an estimate, an honest range and a percentage table.
Works for squat, bench press, deadlift, overhead press and most other lifts. Sets of 3 to 5 reps give the best estimate.
Your numbers stay on your device. We never see them.
Your estimate
Type the weight and reps from your hardest recent set. Your estimated one rep max shows up here.
Check this
Your result
Your estimated one rep max
0kg
What it means
Train with percentages of this number. Do not test it often. It is an estimate for planning, and a hard set of 3 to 5 reps will keep it up to date.
See all 7 formulas
Each formula takes the same set and gives its own answer. Your big number is the average of all 7.
| Formula | Estimate |
|---|
This is education. It is not medical advice. Medical disclaimer.
Percentage table
Example: 100 kg x 5 reps, an estimated max of 115.5 kg. Type your own set above to see yours.
| Percent | Weight | Usual reps to failure |
|---|---|---|
| 100% | 115 kg | 1 |
| 95% | 110 kg | 2 to 3 |
| 90% | 105 kg | 4 to 5 |
| 85% | 97.5 kg | 6 to 7 |
| 80% | 92.5 kg | 9 to 10 |
| 75% | 87.5 kg | 11 to 12 |
| 70% | 80 kg | 14 to 15 |
| 65% | 75 kg | 17 |
| 60% | 70 kg | 19 to 20 |
| 55% | 62.5 kg | 22 to 23 |
| 50% | 57.5 kg | 26 to 27 |
Usual reps are averages from large studies. Leg lifts give more reps than bench, and you may get fewer. Weights are rounded to the nearest 2.5 kg.
What to lift today
Pick the goal that fits. Each card shows a weight range and a rep range.
Strength
87.5 to 105 kg
Heavier loads build the most strength.
Muscle
70 to 92.5 kg
Anything from about 30% to 85% can build muscle if the set is hard.
Endurance
45 to 70 kg
Light weights, many reps.
A starting point, not a rule. If a weight feels very different, trust the bar.
Before you lift
You may not need a 1RM
Our hypertrophy programs run on RPE (how close to failure you train), so you can follow them without a max. This calculator is a handy extra when you want one.
How to test safely
A true max is the riskiest set you can do in the gym. You rarely need one.
- 1Warm up firstDo 2 or 3 lighter sets of the same lift, adding weight each time. Then rest 2 to 3 minutes before your hard set.
- 2Use a spotter or safety barsOn squat and bench, set the safety arms just below your lowest rep. A hard set alone with no catch is how people get pinned.
- 3Use a 3 to 5 rep set instead of a true maxPick a weight you can lift for 3 to 5 reps and go until the next rep would break your form. The estimate is close to a real max and costs far less risk.
- 4Test when you are freshDo it first in the session, not after 10 sets of something else. Tired muscles give a low number.
- 5Same lift, same formUse the same depth and the same pause every time. If the form changes, you are comparing two different lifts.
A calculator cannot see your form, your joints or your health.
Skip a true max if you are new to lifting, hurt, or training alone. Stop the set if you feel a sharp pain in a joint. A burn in the muscle is normal. Under 18? Ask a coach or a parent before heavy lifting. If you have a health condition, ask your doctor first.
This tool is education. It is not medical advice. Read the medical disclaimer.
Under the hood
How we calculate it
Researchers and coaches have published many formulas for turning a set into a max. Each was fitted to a different group of lifters. None of them is right for everyone.
So this page runs 7 of them on your set and averages the results. That average is the big number. Averaging is a simple, sensible choice. I can't tell you it beats the best single formula, because I haven't seen proof of that.
The range under it runs from the lowest formula to the highest. That is just where the formulas disagree. It is a hint about how shaky the number is, and it does not promise your real max sits inside it.
With 1 rep there is nothing to estimate, so your max is the weight you lifted. The limit is 12 reps. At 12 reps the lowest and highest formula are already about 12% apart. At 15 reps it is about 22%.
The 7 formulas
- Epley
- The most used one. Adds a fixed slice of your weight for every rep.
- Brzycki
- Very popular. Works best for sets of 10 reps or fewer.
- Lombardi
- Tends to give higher numbers on sets with more reps.
- O'Connor
- A simple, cautious formula. Often the lowest of the seven.
- Mayhew
- Built from bench press tests. A curve rather than a straight line.
- Wathen
- Similar to Mayhew. Also a curve, a little more careful.
- Lander
- Close to Brzycki. Climbs faster once the reps go up.
How reliable is the number?
- 1 to 5 reps
- Good. Usually within about 5%.
- 6 to 10 reps
- Fair. Usually within 5 to 10%.
- 11 to 12 reps
- Rough. Can be off by 10% or more.
These are rules of thumb from studies, not promises. Your own number can be further off.
The percentage table
The usual reps come from a2024 review of about 7,000 people. They are averages, and people differ a lot. Most lifters get 1 to 3 more reps than the old printed charts say. Leg lifts give more reps than bench. Weights are rounded to the nearest plate jump: 2.5 kg, or 5 lb. The bar for the plate hint is 20 kg, or 45 lb.
Questions
One rep max calculator FAQ
What is a one rep max?
Your one rep max (1RM) is the most weight you could lift once on one exercise with good form. It is different for every lift. Your squat 1RM tells you nothing about your bench 1RM. It also changes with sleep, food and how fresh you are on the day.
How can I find my 1RM without lifting a max?
Do one hard set of 3 to 5 reps. Stop when the next rep would break your form. Type the weight and reps into the calculator. It works out an estimate for you. This is much safer than going for a single, and it is usually close enough to plan your training.
How accurate is a one rep max calculator?
It is an estimate, not a measurement. Usually within about 5% for sets of 1 to 5 reps, and 5 to 10% for sets of 6 to 10. Past 10 reps the guess gets rough, because stamina starts to matter as much as strength. That is why this page shows a range under the number.
How many reps should I use for the estimate?
Use 3 to 5 reps if you can. Take the set close to the end, with maybe 0 or 1 rep left. If you stop with 3 or 4 reps still in the tank, the calculator will guess too low. Being honest about how hard the set was matters more than the exact rep count.
How many reps can I do at 80 percent of my max?
On average people get about 8 to 10 reps at 80 percent, many between 7 and 12, but it varies a lot. It also changes by exercise. Upper body lifts like bench tend to give fewer reps than leg press. Use the table as a rough guide, not a rule.
Should beginners test a true one rep max?
No. Your technique is still settling and you get stronger every week, so the number is old very fast. A heavy set of 5 gives you what you need. Spend the first months learning the lifts and adding weight slowly.
How do I test a true max more safely?
Warm up well, then work up in small jumps with long rests, no more than about 5 singles. Use a spotter or set the safety bars just below your lowest rep. Stop if your form changes or something hurts. If you train alone, safety bars are a must, not an extra.
How often should I update my one rep max?
Every 6 to 12 weeks is plenty. You do not need a max test. Just type in your best recent hard set. If your usual weights suddenly feel easy, update sooner. Do not chase the number every week.
This tool is education. It is not medical advice. Read the medical disclaimer. Last updated: 16 October 2026.
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