What a one rep max estimate means
Your one rep max, or 1RM, is the heaviest load you could lift once with acceptable technique on a given exercise. Finding it directly means attempting a maximal lift, which takes warm-up, equipment, a spotter and a good day, and which is not suitable for everyone. So many lifters estimate it from a set they have already finished. You lift a load for some number of repetitions, enter both numbers, and a formula projects the single-repetition load that the set suggests. For a set of 100 kg for 5 repetitions, the three formulas on this page give 116.7 kg, 112.5 kg and 117.5 kg.
Treat the answer as an estimate and nothing more. The formulas were fitted to groups of lifters, mostly on a few common exercises, and your own relationship between load and repetitions may differ. It depends on the exercise, your training history, how fresh you were, how strict the repetitions were and where you stopped. An estimate is useful for choosing sensible working loads and for comparing one set with another over time. It is not a promise that you could lift that weight today, and the page does not tell you to try.
How to enter a completed set
Enter the load you lifted and the number of repetitions you completed, as a whole number from 1 to 10. The load should be the total external load. For a barbell lift, that means the plates and the bar together, not only the plates. For dumbbell or single-limb work, pick one convention and keep to it: either the weight in one hand or the total of both, and use the same one every time you compare results. The calculator cannot know which you meant, so mixing them will make your numbers meaningless.
Count only the clean repetitions you completed with a consistent range of motion. A set taken to the point where you could not do another is the most informative, because the formulas assume the set was hard. A set of 5 that felt easy will give an estimate that is too low. You can enter the load in kilograms or pounds. The page converts with 1 lb = 0.45359237 kg, keeps the exact value when you switch units, and shows the result in the unit you chose. The lift menu (bench press, squat, deadlift, overhead press or other) only changes the labels on the page. It does not change any coefficient, and it is not stored or sent anywhere.
How hard the set was matters more than most people expect. Lifters sometimes describe this as repetitions in reserve, meaning how many more clean repetitions they could have done when they stopped. A set of 5 with three repetitions still in reserve is closer to a set of 8 in terms of what your muscles can do, so a formula fed that set will understate your capacity. The estimate is only as honest as the input. If you want comparable numbers, stop each logged set at a similar point, ideally close to the limit of what you could repeat with good form, and note that standard next to the result.
Conditions also move the number from one session to the next. Sleep, food, a different bar, a different gym, the time of day, how long you rested between warm-up sets and how many sets came before this one all change what you can lift. None of that shows up in the formula. Record the set under the same conditions each time when you can, and treat a single unusual day as one data point and not as a new level of strength.
Compare Epley, Brzycki and Lombardi
The three formulas answer the same question with different shapes. For two or more repetitions, they use the load W and the repetitions r as follows. With one repetition, every formula simply returns the load you entered, and the page says so, because applying a formula to a single repetition would inflate it for no reason.
Epley
Epley estimates the 1RM as W × (1 + r ÷ 30). Each repetition adds one thirtieth of the load, so the estimate rises in a straight line as repetitions go up. For 100 kg and 5 repetitions it gives 100 × (1 + 5 ÷ 30) = 116.67 kg, and for 10 repetitions it gives 133.33 kg.
Brzycki
Brzycki estimates the 1RM as 36 × W ÷ (37 − r), published in 1993 for predicting a maximum from repetitions to fatigue (Brzycki, 1993). Its denominator shrinks as r grows, so the curve bends upward and the estimate climbs faster at high repetitions. For 100 kg and 5 repetitions it gives 112.50 kg, and for 10 repetitions 133.33 kg. Some publications print rounded coefficients, W ÷ (1.0278 − 0.0278 r), which is nearly the same thing. This page uses the 36 ÷ (37 − r) form, and a small difference between the two is only rounding.
Lombardi
Lombardi estimates the 1RM as W × r^0.1, a power of the repetitions. It grows more slowly than the other two, so for 100 kg and 5 repetitions it gives 117.46 kg and for 10 repetitions 125.89 kg. The three agree closely at moderate repetitions and drift apart as repetitions increase. The named equations here follow the table in a 2008 University of Pittsburgh thesis that compared them (Brennan, 2008). The original Epley and Lombardi papers were not retrieved for this page.
No single one of these is correct for everyone, so the page shows all three at once and lets you pick the one that drives the headline and the tables. Choose one and use it consistently if you are tracking progress, and do not switch to whichever gives the biggest number.
It helps to understand why the three equations disagree. Epley adds a fixed fraction of the load for every repetition, so its estimate climbs in a straight line. Brzycki divides by a number that shrinks as repetitions rise, which makes the estimate accelerate at higher repetitions. Lombardi raises the repetitions to a small power, so it grows steadily but more slowly than the others once the set gets longer. At 1 repetition all three agree by construction, and the gap between them opens as repetitions increase. That is why a tracking log should name the formula and the repetition count along with the estimate.
Worked bench, squat and deadlift examples
Here are three sets, with the arithmetic worked out. These are made-up sets, chosen only to show the method. A lifter bench presses 80 kg for 6 repetitions. Epley gives 80 × (1 + 6 ÷ 30) = 96.00 kg. Brzycki gives 36 × 80 ÷ (37 − 6) = 92.90 kg. Lombardi gives 80 × 6^0.1 = 95.70 kg. The estimates span 3.10 kg, which is a fair indication of how uncertain the single figure is.
A second lifter squats 120 kg for 5 repetitions. Epley gives 140.00 kg, Brzycki gives 135.00 kg and Lombardi gives 140.95 kg. A third deadlifts 140 kg for 3 repetitions, and the estimates are 154.00 kg, 148.24 kg and 156.26 kg. At 3 repetitions the three methods are within about 8.0 kg of each other, a tighter spread than at 6.
The arithmetic is the same for every exercise, because the formulas do not know which lift you did. What differs is how well each formula fits that lift in people like you, which is why the page treats the result as an estimate for one exercise, and not a number to carry from the bench press to the squat. Pounds work the same way. A set of 225 lb for 5 repetitions is 102.06 kg, and Epley gives 119.07 kg, or 262.5 lb. If you want to see how the lean mass of a lifter compares across formulas, the lean mass estimates page is a separate tool, and the two are not connected.
Here is a small example of tracking. Suppose a lifter squats 100 kg for 5 repetitions in one session and, several weeks later, 102.5 kg for 5 repetitions. With Epley the first set gives 116.67 kg and the second 119.58 kg, a difference of 2.92 kg. Because both sets use the same formula and the same number of repetitions, the comparison is fair, and the change reflects the extra 2.5 kg that was lifted and not a change in method. The gap is small compared with the spread between formulas, so it would be unwise to read much into one pair of sets. A trend over several sessions says more than any single comparison.
Read the load chart and percentage table
Below the formula comparison, the page shows a table of loads at 50% to 100% of the estimated maximum, in steps of five points. Every row is calculated from the unrounded estimate. With the Epley estimate of 116.67 kg from the 100 kg by 5 example, 75% is 87.50 kg. You can ask the page to round those loads to the nearest 1 kg, 2.5 kg or 5 lb. The rounding applies only to the displayed loads, so it never changes the estimate itself. Rounding the 75% load to the nearest 2.5 kg gives 87.5 kg.
The table reads one way: pick a percentage and see the load. It does not say how many repetitions you can do at that load, and the page deliberately has no such column. Two lifters with the same 1RM can differ a great deal in how many repetitions they can do at 75%. The second display is the rep-load curve, which turns the idea around. It starts from the estimated maximum and shows the load that each formula associates with 1 to 20 repetitions. With Epley and the 116.67 kg estimate, the 3-repetition load is 106.1 kg, the 8-repetition load is 92.1 kg and the 5-repetition load returns 100.0 kg, the load you entered. The curve is drawn with the same data as a table beside it, so the numbers are available without the picture.
Why higher-rep estimates are less certain
The input is limited to 10 repetitions, and the reason is uncertainty. The more repetitions you do, the further the set sits from a single maximal effort, and the more other factors matter: muscular endurance, pacing, breathing, grip, fatigue and motivation. Formulas fitted at low and moderate repetitions are stretched when they are applied to a set of 15 or 20. Different formulas also diverge: at 10 repetitions, the three estimates for 100 kg are 133.3, 133.3 and 125.9 kg, and the gap keeps widening beyond that.
The curve does go to 20 repetitions, but only as an illustration. Rows beyond 10 are labelled as an extrapolated illustration in the table and shown with a dashed line and open dots on the chart. For example, Epley's curve for the 116.67 kg estimate gives 77.8 kg at 15 repetitions and 70.0 kg at 20. These are mathematical consequences of the equation. They are not predictions of what you can do, and they should not be used to set a training load.
There is a further reason to be careful beyond the heavy end of the range. Fatigue dominates a long set, and the formulas were built around the idea that the final repetition is close to the limit. When a set of 12 ends because your grip gave out or your breathing failed, the result describes endurance of that muscle group, not the largest load you could move once. A set of 10 is not a clean substitute for a set of 3, even when the arithmetic produces a similar estimate, and the page keeps the input at 10 repetitions or fewer so that the result never pretends otherwise.
Tracking comparable sets and choosing units
The most reliable use of an estimate is to compare like with like over time. Use the same exercise, the same formula, the same repetition standard and about the same number of repetitions each time. If one estimate comes from a set of 3 and the next from a set of 10, part of the difference you see comes from the formula and not from your strength. A change that is smaller than the spread between formulas is within the noise of the method.
Pick the unit your equipment uses. Kilogram plates and pound plates do not line up neatly, which is why the page offers rounding to 1 kg, 2.5 kg or 5 lb. The estimate is stored internally in kilograms and converted for display, so changing the unit does not change the number, apart from the digits you see. If you also want a record of the energy cost of a session, see the activity calorie estimates page, which treats resistance training with a single MET value and does not use your 1RM at all. The two numbers answer different questions.
A practical way to use the percentage table is to plan the loads for a session from a recent estimate and then adjust by feel. Many programmes describe working sets as a percentage of a maximum, and the table gives you the numbers for those percentages in one place. If a load that the table calls 75% feels much easier or harder than the programme intends, that tells you the estimate is off for that exercise today, and the sensible response is to adjust the load rather than defend the number. Estimates should serve the training, not direct it.
Keep the estimate separate from the training log of what you actually lifted. The log of loads and repetitions is the real record. The estimate is a derived figure that depends on a formula, so it is better written beside the raw sets than in place of them. If you later change formula or want to recompute older sets, the raw sets let you do that, and the estimates alone would not.
Limits of estimates and maximal testing
These formulas know nothing about your technique, injuries, sleep, programme or equipment. They do not know whether a bench set was paused or bounced, or whether a squat reached depth. A calculator cannot give you strength standards, tell you which programme to follow or confirm that a load is safe. It also cannot say how many repetitions you could do at a given percentage. An estimate that is too high can lead to a load that is too heavy for your next set, so cross-check it against how recent sets actually felt.
The page does not recommend attempting a maximal single. A true maximum is a high-risk effort, and people with joint, heart or blood pressure concerns, beginners, and anyone training alone have good reasons to avoid it. If testing a maximum matters to your sport, plan it with a coach, use spotters or safety bars, and build up gradually. If you are unsure whether it is appropriate for you, speak to a qualified professional. Nothing on this page is medical or coaching advice.
Equipment and technique standards change the meaning of a maximum. A bench press with a pause on the chest is a different lift from a touch-and-go repetition, and a squat to full depth is a different lift from a partial squat. Powerlifting federations and gyms apply different standards, so two people can report the same load for what are in practice different movements. Decide on your own standard, apply it every time, and avoid comparing your estimate with figures from people who may have used a different one. Those comparisons say little about either of you.
Age, training experience and sex also affect how load and repetitions relate, and the formulas on this page do not take any of them as inputs. Beginners often gain strength quickly, so an estimate can go out of date within weeks. Experienced lifters change slowly, which makes small differences harder to interpret. Whatever your situation, return to the same few questions: was the set hard, were the repetitions clean, and is the comparison with an earlier set fair.
Sources and conventions
The three equations are used as defined above, with weights in kilograms internally, r from 1 to 10 for the estimate, and the single-repetition rule that returns the load unchanged. Brzycki's published form is cited from the 1993 article and its author record, and the named equation table follows a university thesis that compared the formulas. Coefficient variants exist in the literature, and small differences between calculators usually come from those variants or from rounding. Sources were checked on 8 November 2026. For the protein side of strength training, the compare protein references page puts adult protein recommendations side by side.
One rep max questions
How do I calculate my 1RM?
Enter the load and the repetitions of a recent hard set. With Epley, multiply the load by one plus the repetitions divided by 30. A set of 100 kg for 5 repetitions gives 100 × (1 + 5 ÷ 30) = 116.67 kg. The page also shows Brzycki (112.50 kg) and Lombardi (117.46 kg) for the same set.
Can I use bench, squat and deadlift results?
Yes. The arithmetic is the same for every exercise, but each estimate describes only that lift. A bench press estimate says nothing reliable about your squat, and the lift menu on the page changes labels only.
Which formula should I choose?
There is no universally best choice. Compare the three, pick one, and keep using it so that your results stay comparable. Do not switch formulas to reach a larger number.
What if I completed one repetition?
Then the load you lifted is your one rep max for that set, so the page returns it unchanged for every formula and labels it as one completed repetition.
Why limit the input to 10 repetitions?
Uncertainty rises as repetitions increase and the three formulas diverge. The curve shows 11 to 20 repetitions only as an extrapolated illustration, clearly labelled.
Does a percentage tell me exactly how many reps I can perform?
No. The number of repetitions you can do at a given percentage varies from person to person and from exercise to exercise, so the percentage table shows loads, not repetition counts.