Strength Guide
How to Calculate One Rep Max
Your how to calculate one rep max is the heaviest weight you can lift once with good form. It is the number every serious program is built on — and you do not need to risk a true max attempt to find it. This guide shows you how to calculate your 1RM from a normal training set, which formula to trust, and how to test it safely when you are ready.
Updated: November 7, 2026.
The Basics
What Is a One-Rep Max?
A one-rep max, or 1RM, is the heaviest weight you can lift for one single repetition with good form. If you can bench 100 kg once and no more, your bench press 1RM is 100 kg. If you squat 140 kg for one clean rep, your squat 1RM is 140 kg. Every lift has its own 1RM — there is no single number for your whole body.
Coaches use your 1RM as the anchor for your whole program. Instead of guessing what weight to load, they write your training as a percentage of your max: 80% for strength work, 70% for volume, 90% for a heavy top set. Once you know your max, every set has a clear purpose, and you can track real progress instead of hoping the weight feels right.
Your 1RM also gives you a way to compare lifts and lifters. A 120 kg bench means more for a 70 kg lifter than for a 110 kg lifter, which is why strength is usually judged against bodyweight. Our strength standards calculator shows you where your lifts sit for your bodyweight, and our RPE calculator lets you work backwards from a training set to your estimated max.
If you already know a recent set — say 100 kg for 5 reps — you do not need to test a max at all. You can estimate it with a formula, or use our rep range to 1RM converter to turn any rep range into a max estimate in seconds.
The Math
The 7 One-Rep Max Formulas, Compared
Seven formulas dominate 1RM estimation, and they all do the same job: they take the weight and reps from a set you already did and predict the weight you could lift once. They disagree by a few kilograms, because each one was built from different lifters and different data. Here they are, side by side, all applied to the same set — 100 kg for 5 reps — so you can see the spread for yourself.
| Formula | Equation | 100 kg x 5 reps | Best For |
|---|---|---|---|
| Epley (1985) | 1RM = weight x (1 + reps / 30) | 116.7 kg | Most lifters, most lifts |
| Brzycki (1993) | 1RM = weight x 36 / (37 – reps) | 112.5 kg | Low rep sets (1 to 6 reps) |
| Lander (1985) | 1RM = weight x 100 / (101.3 – 2.67123 x reps) | 113.7 kg | General use |
| Lombardi (1989) | 1RM = weight x reps^0.10 | 117.5 kg | Higher rep sets |
| Mayhew (1992) | 1RM = weight x 100 / (52.2 + 41.9 x e^(-0.055 x reps)) | 119.0 kg | Trained lifters |
| O’Conner (1989) | 1RM = weight x (1 + 0.025 x reps) | 112.5 kg | Quick estimates |
| Wathan (1994) | 1RM = weight x 100 / (48.8 + 53.8 x e^(-0.075 x reps)) | 116.6 kg | General use |
The seven answers run from 112.5 kg to 119.0 kg — a spread of 6.5 kg, or about 5.6 percent. The average is 115.5 kg. That spread is honest, not a flaw: no formula can know your technique, your fatigue, or your fiber mix. Treat the answer as a range, not a single magic number.
Which one should you use? For most lifters, Epley is the safe default — it is simple, widely used, and sits in the middle of the range. Brzycki and O’Conner run a little low, Mayhew runs a little high, and the rest cluster near the average. Pick one formula and stick with it, so your progress is measured the same way every time. Our 1RM formulas explained guide walks through each formula in full detail, with its history and its limits.
Check the Math
Worked Examples You Can Check
Example 1: 100 kg for 5 reps
Take a lifter who benches 100 kg for 5 reps. Epley says: 100 x (1 + 5 / 30) = 100 x 1.1667 = 116.7 kg. Brzycki says: 100 x 36 / (37 – 5) = 100 x 36 / 32 = 112.5 kg. The other five formulas land between 113.7 kg and 119.0 kg, and the average of all seven is 115.5 kg. So this lifter’s bench press 1RM is about 113 to 119 kg — call it 115 kg for programming, and use 92 to 103 kg for working sets at 80 to 90 percent.
Example 2: 80 kg for 8 reps
Now a lifter who squats 80 kg for 8 reps. Epley gives 80 x (1 + 8 / 30) = 80 x 1.2667 = 101.3 kg. Brzycki gives 80 x 36 / (37 – 8) = 80 x 36 / 29 = 99.3 kg. The two formulas agree within 2 kg here, which is typical for sets of 6 to 10 reps. An estimated squat max of about 100 kg is a solid number to program from.
Example 3: 225 lb for 5 reps
If you train in pounds, the math is identical — just keep the units the same. A lifter who benches 225 lb for 5 reps gets 225 x (1 + 5 / 30) = 262.5 lb with Epley, and 225 x 36 / 32 = 253.1 lb with Brzycki. That is roughly a 255 to 263 lb max. The same set at RPE 8 would point to a similar number — our rate of perceived exertion calculator shows you how effort ratings and formulas line up, and if you compete, our powerlifting total calculator turns your three lift maxes into a meet total.
Test Day
How to Test Your 1RM Safely
Formulas estimate your max. A test proves it. Follow these steps and the test is honest without being reckless.
Step 1: Pick the right day
Test when you are fresh — after a rest day or a light day, not at the end of a hard week. Eat normally, sleep well the night before, and test early in the session, before any fatigue builds up.
Step 2: Warm up in stages
Start with the empty bar for 8 to 10 reps, then add weight in big jumps while the weight is light: 40% for 5 reps, 60% for 3 reps, 75% for 2 reps, 85% for 1 rep. Your warm-up should leave you warm, not tired.
Step 3: Build up in small jumps
Above 85%, take jumps of 2.5 to 5 kg on upper-body lifts and 5 to 10 kg on lower-body lifts. Big jumps waste attempts; tiny jumps waste energy. Each single should feel like a confident step, not a gamble.
Step 4: Take three attempts at most
You get three real attempts near your max. If you miss a weight, you are done for the day — a fourth attempt after a miss is how injuries happen. Your best completed lift is your 1RM.
Step 5: Use a spotter and safety bars
Never test a bench press alone. A spotter stands behind you, hands ready, and the safety pins are set just below chest level. For the squat, set the safety bars so you can dump the bar safely. For the deadlift, use a flat floor and a bar that will not roll.
Step 6: Rest 3 to 5 minutes between attempts
Heavy singles need full recovery. Rest at least 3 minutes, 5 minutes if the last attempt was a grinder. Rushing the rest is the most common reason a test day fails.
The same steps work for every lift — our bench press 1RM guide, squat 1RM guide, and deadlift 1RM guide walk through the setup and the common faults for each one.
Program With It
1RM Percentages for Training
Once you know your max, percentages turn it into a plan. Here is what each percentage looks like for a lifter with a 200 kg max, and how many reps you can usually do at that load.
| Percentage of 1RM | Weight (200 kg max) | Typical Reps |
|---|---|---|
| 100% | 200 kg | 1 |
| 95% | 190 kg | 2 |
| 90% | 180 kg | 4 |
| 85% | 170 kg | 5 |
| 80% | 160 kg | 6 |
| 75% | 150 kg | 8 |
| 70% | 140 kg | 10 |
| 65% | 130 kg | 12 |
| 60% | 120 kg | 15 |
| 50% | 100 kg | 20+ |
Percentages also define your training zones. Strength lives at 85 to 100% of your max, for 1 to 6 reps. Muscle growth lives at 65 to 85%, for 6 to 12 reps. Endurance lives at 50 to 65%, for 12 reps and more. Most good programs spend most of their time in the strength and growth zones, and visit the top end only for testing or peaking.
| Training Goal | Percentage of 1RM | Reps per Set |
|---|---|---|
| Max strength | 85-100% | 1-6 |
| Muscle growth | 65-85% | 6-12 |
| Muscular endurance | 50-65% | 12+ |
Percentages are a starting point, not a prison. If 80% feels like 90% on a bad day, drop the weight and hit the reps — the stimulus matters more than the number on the bar. Our strength training fundamentals guide explains how percentages, volume, and frequency fit together, and if you are preparing for a meet, our powerlifting competition guide shows how to peak your percentages into attempt selection.
Stay Current
When to Retest Your 1RM
Your max is a moving number. Retest every 8 to 12 weeks, or at the end of a training block, and you will catch your gains while they are fresh. Beginners can retest more often — every 6 to 8 weeks — because their numbers climb fast. Advanced lifters retest less often, because their progress is slower and a max test costs more recovery.
You do not always need a test day. If you hit a new 5-rep best, your max went up — run the formula and update your training numbers. That is the smarter way to stay current: let your training sets tell you when your max moved, and save the true max test for the end of a block or the week before a competition.
Recovery shapes your max as much as training does. Sleep, food, and rest weeks all show up in the number on the bar. Our nutrition and recovery for strength guide covers what to eat and how to recover so your next test shows your real strength, and our strength standards benchmarks guide tells you what a good max looks like for your bodyweight and experience level.
Avoid These
Common Mistakes to Avoid
- Testing too often. A max test is a workout by itself. Test every week and you spend your recovery on testing instead of training.
- Using high-rep sets to estimate. Formulas are built for sets of 10 reps or fewer. A 20-rep set can overestimate your max by 10 percent or more.
- Switching formulas every week. Different formulas give different answers. Pick one, use it for the whole block, and your progress stays comparable.
- Counting a sloppy rep. A max with a bouncing chest, a hitched deadlift, or a half squat is not a max. If the form breaks, the rep does not count.
- Skipping the warm-up. Jumping to heavy singles cold is the fastest way to a pulled muscle and a failed test day.
- Training at your max all the time. Your 1RM is a reference number, not a daily target. Most training should sit at 65 to 85 percent.
If you want a single place to keep all of this straight, start from our strength calculators home page — every tool and guide on this site links back to it.
Questions
Frequently Asked Questions
What is a one-rep max?
A one-rep max, or 1RM, is the heaviest weight you can lift for one repetition with good form. If you can bench 100 kg once and no more, your bench press 1RM is 100 kg. Every lift has its own 1RM.
How do you calculate your 1RM without testing it?
Lift a weight you can manage for 1 to 10 reps, then use a formula. The Epley formula is the most common: 1RM equals weight times (1 + reps / 30). So 100 kg for 5 reps gives about 116.7 kg. You can also use our rep range converter to do the math for you.
Which 1RM formula is the most accurate?
No single formula wins for everyone. Epley is the best default for most lifters, Brzycki works well for low-rep sets, and Mayhew fits trained lifters. The seven main formulas agree within about 5 percent on sets of 5 reps or fewer, so pick one and use it consistently.
How accurate is a 1RM estimate?
From a recent set of 1 to 6 reps, a formula estimate is usually within 2 to 5 percent of your true max. The estimate gets less reliable above 10 reps, and it cannot account for a bad day, poor sleep, or sloppy form. Treat it as a range, not an exact number.
How often should you test your 1RM?
Every 8 to 12 weeks, or at the end of a training block. Beginners can test every 6 to 8 weeks because their strength climbs fast. Between tests, update your max from your best training sets instead of testing again.
Can you calculate your 1RM from 10 reps?
Yes, but the answer is less reliable. Formulas are built for sets of 10 reps or fewer, and the error grows as reps climb. A 5-rep set gives a much better estimate than a 10-rep set, and a 20-rep set can overestimate your max by 10 percent or more.
What percentage of your 1RM should you lift for strength?
Train at 85 to 100 percent of your 1RM for 1 to 6 reps to build max strength. For muscle growth, use 65 to 85 percent for 6 to 12 reps. Most of your training should sit in those two zones, with the top end reserved for testing and peaking.
Is it safe to test your 1RM alone?
No, not for the bench press or the squat. Always use a spotter and safety bars, and never test a max when you are tired, sick, or rushed. The deadlift is the safest lift to test alone, because you can simply drop the bar.