One Rep Max Calculator: Estimate Your 1RM
Enter the weight you lifted and how many reps you did. This one rep max calculator estimates your 1RM with the Epley formula, compares six other formulas and gives a percentage table.
By Troopus · Updated: October 28, 2026
- 2 inputs
- lb or kg
- 7 formulas
- 100% private
1RM calculator
| Formula | Estimated 1RM |
|---|
| % of 1RM | Weight | About reps |
|---|
Estimate for information only. Not medical or training advice. Actual strength varies by lift, form and day. Rep counts per percentage are a rough guide. Lift safely, use a spotter, and ask a qualified coach or doctor if unsure.
How does a one rep max calculator work?
To estimate your one rep max, lift a weight for several reps (ideally 2 to 10) and put the weight and reps into a formula such as Epley. For example, 185 lb for 5 reps gives 185 x (1 + 5/30) = about 215.8 lb. The calculator above does it as you type.
A one rep max (1RM) is the heaviest weight you can lift once with good form. Testing it directly means loading the bar until you fail, which takes time and carries more risk. Wikipedia notes that a submaximal estimate is safer and quicker than a formal test, and that it is best used as a starting point. So the usual approach is to do a hard set of a few reps and estimate.
| Set | Working | Estimated 1RM |
|---|---|---|
| 135 lb x 8 | 135 x (1 + 8/30) | 171.0 lb |
| 185 lb x 5 | 185 x (1 + 5/30) | 215.8 lb |
| 225 lb x 3 | 225 x (1 + 3/30) | 247.5 lb |
What are the Epley formula and the Brzycki formula?
The Epley formula is 1RM = weight x (1 + reps / 30). It was published by Boyd Epley in 1985 and is one of the most widely used rep max formulas. This calculator uses it as the headline result and lists six others, such as Brzycki, so you can compare them for the same set.
All of these formulas take your weight (w) and reps (r) and return an estimate. For a single rep each simply returns your weight. The table lists the versions used here, as given in the Wikipedia article on the one-repetition maximum.
| Formula | Equation |
|---|---|
| Epley | w x (1 + r / 30) |
| Brzycki | w x 36 / (37 - r) |
| Lombardi | w x r ^ 0.10 |
| Mayhew | w / (0.522 + 0.419 e ^ (-0.055 r)) |
| O'Conner | w x (1 + 0.025 r) |
| Wathen | w / (0.488 + 0.538 e ^ (-0.075 r)) |
| Landers | w / (1.013 - 0.0267123 r) |
Epley and Brzycki give the same result at 10 reps. Below 10 reps, Epley gives a higher estimate. Brzycki comes from Matt Brzycki's 1998 book, A Practical Approach To Strength Training. The formulas spread out noticeably as reps climb, which is why the calculator shows the range for your set.
The Brzycki formula divides the weight by 1.0278 minus 0.0278 times the reps, and it gives slightly different answers from Epley at higher rep counts.
How do you estimate your max bench press?
Do a hard set of 3 to 8 reps on the bench press, then enter that weight and the reps you completed. If you press 185 lb for 5 reps, the bench press calculator estimates a max bench of about 216 lb with Epley. Use the same method for any lift.
The formulas do not know which exercise you did, so the same calculator works as a max bench calculator, a squat calculator or a deadlift calculator.
How accurate is a one rep max calculator?
A 1RM calculator gives an estimate, and it can be off by 10% or more from your true max. Accuracy is best from sets of about 2 to 10 reps and worsens above 10, where the formulas diverge. Treat the number as a starting point for planning, not a guaranteed max.
Wikipedia says estimates may vary by 10% or more from the actual 1RM, and that the formulas diverge greatly after about 10 reps. That is why the calculator warns you when you enter more than 10 reps and refuses more than 30.
What are the percentages of 1RM?
Percentages of 1RM turn your max into training weights, such as 80% of 1RM for sets of about 8 reps. The table in the calculator lists 95% down to 50% of your estimated max with a rough rep guide. Lifters often use heavier percentages for strength and lighter ones for higher reps.
Here is the table for a 215.8 lb estimate, which is the 185 lb x 5 example. The rep column is a rough guide that this calculator works out by turning the Epley formula around: reps = 30 x (1 / percent - 1). Real rep counts differ from person to person and lift to lift, so adjust by feel.
| % of 1RM | Weight | About reps |
|---|---|---|
| 95% | 205 lb | 2 |
| 90% | 194 lb | 3 |
| 85% | 183 lb | 5 |
| 80% | 173 lb | 8 |
| 75% | 162 lb | 10 |
| 60% | 130 lb | 20 |
| 50% | 108 lb | 30 |
Percentages are also easy to work out with the percentage calculator.
Frequently asked questions
What is a 1RM?
A 1RM, or one rep max, is the most weight you can lift for a single repetition of an exercise with correct form. It is used to set training loads as percentages. Most people estimate it from a set of several reps.
What is the best 1RM formula?
No single formula is best for everyone. Epley and Brzycki are the most commonly used and agree closely at 10 reps. Because estimates vary by lift and rep count, this calculator shows seven formulas so you can compare them.
How many reps should I use to estimate my 1RM?
Use a hard set of roughly 2 to 10 reps, with fewer reps giving a more reliable estimate. Above 10 reps the formulas disagree more and the result is less trustworthy. Stop each set before your form breaks down.
How do I calculate a rep max for other rep counts?
Turn the Epley formula around: weight for n reps = 1RM / (1 + n / 30). With a 216 lb max, a 10-rep weight is 216 / 1.333 = about 162 lb. The percentage table above gives these as a rough guide.
Is it safe to test a true one rep max?
It can be, when done with warm-up sets, good form, rest between attempts and a spotter or safety bars. Wikipedia notes there is a risk of injury if you are unfamiliar with proper form. Estimating from a lighter set is safer.
Can I use this for squat and deadlift?
Yes, the formulas only use weight and reps, so they work for any lift. Accuracy can differ by exercise, so treat the result as a rough guide and build up to heavy weights carefully.
Why does the calculator reject more than 30 reps?
Strength formulas were built from heavy sets and become meaningless for very long sets. At 30 reps the Epley estimate is already double your weight. If you did more than 30 reps, use a heavier weight for a better estimate.
Should I enter pounds or kilograms?
Either. Use the lb or kg switch and the results use the same unit. The formulas are unit-free, so 100 kg for 5 reps gives the same percentage uplift as 100 lb for 5 reps.