Free one rep max calculator

How to use the one rep max calculator

This one rep max calculator turns one hard set into an estimate of the most you could lift for a single rep. It takes about ten seconds and needs no max attempt.

1. Choose lb or kg, and pick your lift. The lift only changes the labels and the accuracy note. The maths is the same for every lift.
2. Enter the total weight on the bar, bar included. Check your bar’s stated weight; they are not all the same.
3. Enter the reps you finished with good form. The calculator accepts 1 to 12 reps and warns you above 10.
4. Read the average estimate, the range across all seven formulas, and the percentage chart below it.

The page link updates as you type, so you can save or share your numbers.

What is a one rep max?

A one rep max (1RM) is the heaviest weight you can lift once, with full range of motion and good form. It is the standard way coaches measure maximal strength for a single exercise.

Your 1RM is specific to the lift, and it changes as you train, rest and recover.

There are two ways to find it:

• Test it. Warm up, then work up to one heavy single you cannot beat. This is the most direct answer, but it takes time, energy and a safe setup.
• Estimate it. Lift a lighter weight for several reps close to failure, then plug the numbers into a 1RM calculator. This is faster and lower risk, but it is only an estimate.

The 2006 study by Reynolds, Gordon and Robergs in the Journal of Strength and Conditioning Research notes that for some people, age and existing medical conditions can make a true max test unsafe. That is one of the main reasons estimation formulas exist.

The 1RM formulas this calculator uses

This 1RM calculator runs seven published equations and shows each result, then uses their average as the headline number. Averaging smooths out the quirks of any one formula.

In the table, w is the weight lifted and r is the number of reps. Each equation below matches the form printed in the Reynolds 2006 study and in Wikipedia’s one-repetition maximum entry. The recommended rep limits come from the Reynolds paper’s table notes.

Formula	Equation	Recommended rep range
Epley	1RM = w × (1 + r ÷ 30)	Under 10 reps
Brzycki	1RM = w × 36 ÷ (37 − r)	Under 10 reps
Lander	1RM = w ÷ (1.013 − 0.0267123 × r)	Not specified
O’Conner	1RM = w × (1 + 0.025 × r)	Not specified
Lombardi	1RM = w × r^0.10	Under 11 reps
Mayhew	1RM = 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r))	Under 15 reps
Wathan	1RM = 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r))	Not specified in the source

The first four are linear. Each added rep adds a fixed chunk to the estimate. Lombardi, Mayhew and Wathan are curved. They add less for each extra rep as the set gets longer.

If you enter 1 rep, the calculator shows the weight itself as your max. A single is already a max for that day. Running it through the equations would add a few pounds for no reason.

How to calculate one rep max by hand: a worked example

Here is a real set: 225 lb on the bench press for 5 reps.

• Epley: 225 × (1 + 5 ÷ 30) = 225 × 1.1667 = 262.5 lb
• Brzycki: 225 × 36 ÷ (37 − 5) = 225 × 36 ÷ 32 = 253.1 lb
• Lander: 225 ÷ (1.013 − 0.1336) = 225 ÷ 0.8794 = 255.8 lb
• O’Conner: 225 × (1 + 0.125) = 253.1 lb
• Lombardi: 225 × 5^0.10 = 225 × 1.1746 = 264.3 lb
• Mayhew: 100 × 225 ÷ (52.2 + 41.9 × 0.7596) = 22,500 ÷ 84.03 = 267.8 lb
• Wathan: 100 × 225 ÷ (48.8 + 53.8 × 0.6873) = 22,500 ÷ 85.78 = 262.3 lb

The average is 259.8 lb, which rounds to about 260 lb. The spread runs from 253 lb to 268 lb. That 15 lb gap is a useful reminder that an estimate is a range, not one exact number.

The same set in metric is 100 kg for 5 reps. The average comes out at about 115.5 kg, with a spread from 112.5 kg to 119 kg.

Which 1RM formula is most accurate?

No single formula wins for every lift and every lifter. Research shows the best choice depends on the exercise and on how many reps you did.

The clearest data comes from a 1997 study by LeSuer and colleagues, summarized in a 2009 paper by Eston and Evans in the Journal of Sports Science and Medicine. It tested seven equations on the bench press, squat and deadlift in new lifters. The results differed a lot by lift, so each one gets its own section below.

The 2006 Reynolds study looked at the chest press and leg press in 70 adults aged 18 to 69. It found all the linear equations worked with similar accuracy on 5-rep sets. Every equation got worse when fed 10-rep data instead of 5-rep data. In that group, the curved Lombardi and Mayhew equations were less accurate than the linear ones.

The two studies disagree on which formula is best. When research can’t name a winner, averaging several good equations is a sensible middle.

One rep max bench press calculator results

The bench press is where these formulas are on the firmest ground. Most of them were built or tested on bench or chest press data. In the 1997 study, the Mayhew and Wathan equations predicted bench press 1RM successfully. If you use the tool as a bench press calculator, look at those two rows next to the average.

For a max bench calculator estimate you can trust, use a pause-free set with the bar touching your chest on every rep. A half-rep set inflates the number.

Squat max calculator: what the research says

For the squat, the 1997 study found that only the Wathan equation predicted 1RM well. That makes the squat max calculator number a little less certain than the bench number.

Depth is the other issue. As a squat set gets hard, many lifters cut depth on the last reps. If rep 5 was higher than rep 1, count 4. Consistent depth matters more than the formula you pick. Our guide to how to use a power rack for squats covers setting the safety arms at the right height for your depth.

Deadlift one rep max calculator: why estimates run low

For the deadlift, every equation in the 1997 study underestimated the true max. The average miss was 22 to 34 lb, or 9 to 14%. Eston and Evans report that the correlation was still high. The formulas ranked lifters in the right order but set the number too low.

In practice, treat a deadlift estimate as a floor. If the calculator says 400 lb, your tested max may be higher. Plan training loads from the estimate anyway. Starting a little light costs little.

Overhead press and other lifts

There is little published data on these equations for the overhead press. Treat that estimate as a rough guide. The same goes for rows, hip thrusts and machine lifts. The Nuzzo meta-analysis did find leg press data, and people did more reps at a given percentage on the leg press than on the bench press. That means the reps column in the chart will read low for the leg press.

Why more reps means a less accurate estimate

The fewer reps in your set, the closer the weight is to your max, and the less the formula has to guess. Long sets add fatigue, breathing and pacing into the mix, which the equations do not model well.

The Reynolds study is direct on this point. It found 5-rep sets predicted 1RM best, and it concluded that no more than 10 reps should be used in linear equations. That is why this tool warns you above 10 reps and stops at 12.

People also vary most at light loads. The Nuzzo meta-analysis of 269 studies found that both the average reps and the spread between people change with load. The spread is larger at lighter loads. Two lifters with the same 1RM might get very different rep counts at 60%, but similar counts at 90%.

The best set for estimating is heavy enough to finish in about 3 to 6 reps and taken close to failure. A set you stop with 4 reps left in the tank will produce an estimate that is far too low.

1RM percentage chart

A 1RM percentage chart turns your max into training loads. Each row shows a percentage of your max, the load, and about how many reps most people can do at that load.

The reps column comes from the National Strength and Conditioning Association (NSCA) training load chart, adapted from Landers (1984). That chart stops at 12 reps and 70%. Below 70%, it gives no figure, so the table says “more than 12”.

This rep max chart uses an estimated 1RM of 260 lb (225 lb for 5 reps) and 115.5 kg (100 kg for 5 reps). Loads are rounded to the nearest 5 lb or 2.5 kg so you can load them on a real bar.

% of 1RM	Load, 260 lb max	Load, 115.5 kg max	Typical max reps (NSCA)
100%	260 lb	115 kg	1
95%	245 lb	110 kg	2
93%	240 lb	107.5 kg	3
90%	235 lb	105 kg	4
87%	225 lb	100 kg	5
85%	220 lb	97.5 kg	6
83%	215 lb	95 kg	7
80%	210 lb	92.5 kg	8
77%	200 lb	90 kg	9
75%	195 lb	87.5 kg	10
70%	180 lb	80 kg	12
65%	170 lb	75 kg	More than 12
60%	155 lb	70 kg	More than 12
55%	145 lb	62.5 kg	More than 12
50%	130 lb	57.5 kg	More than 12

The NSCA chart can also run in reverse. Its own example: if you squat 160 lb for 8 reps, your estimated 1RM is 200 lb. The seven-formula average for that set is 199.6 lb, which is a close match.

Bench press percentage chart: reading it right

A bench press percentage chart is a starting point, not a promise. The Nuzzo meta-analysis built separate tables for the bench press and leg press because reps at the same percentage differed between them. It found that sex, age and training status had little clear effect on the relationship. Exercise choice mattered more.

If the chart says 8 reps at 80% and you get 6, your estimate was probably high, or you were tired that day. Adjust from what the bar tells you.

How to use your 1RM for programming

Your estimated 1RM is most useful as a way to set training loads, not as a score. Most strength programs are written in percentages, so you need a max to turn “5 × 5 at 80%” into a real weight.

The NSCA chart gives a simple link between load and reps:

• Heavy work, about 85% to 100%: 1 to 6 reps. This is the zone for building maximal strength.
• Moderate work, about 70% to 85%: 6 to 12 reps. This covers most muscle-building sets.
• Lighter work, under 70%: more than 12 reps. Useful for technique, warm-ups and endurance.

A few rules make percentage training work better:

• Use a training max if you are unsure. Many programs base their numbers on a max a little below your estimate. This leaves room for bad days.
• Stay close to failure but not at it. The chart’s rep numbers are maximums. Programs usually ask for fewer reps than the chart allows at a given load.
• Re-estimate every few weeks. Any heavy set can give you a new estimate. Enter it and update your numbers.

If you train by effort instead of percentage, our RPE calculator converts reps in reserve into loads. It pairs well with this tool. Once you have a number, the barbell calculator shows which plates to load on each side.

How to test your one rep max safely at home

The safest way to test a true max at home is inside a power rack with the safety arms set, after a planned warm-up, with a spotter if you can get one. If you can’t do all of that, use an estimate instead.

Testing a real max is a reasonable thing to do. The Grgic 2020 systematic review found the 1RM test has good to excellent test-retest reliability, with a median intraclass correlation of 0.97. That held across training levels, lifts, sexes and ages. The test is dependable. The risk is in the setup.

Warm-up sets before a max attempt

The American Council on Exercise (ACE) lays out a simple protocol for a 1RM test:

1. One set of 5 to 10 reps at about 50% of your expected max. Rest 1 minute.
2. One set of 3 to 5 reps at 70% to 75%. Rest 1 minute.
3. One set of 2 to 3 reps at 85% to 90%. Rest 2 to 4 minutes.
4. A first max attempt. Add or remove roughly 5 to 10 lb based on how it moved, and rest 2 to 4 minutes between attempts.

ACE says to find the max in fewer than five attempts, ideally. Past that, fatigue starts to cost you. Use the percentage chart from this calculator to plan each warm-up load before you start.

Set up your rack and safety arms

For the squat and bench press, a rack with safety arms is the most important piece of kit. Set the arms just below the lowest point of your rep. That way, a failed rep settles onto the steel, not onto you.

• Squat: Set the arms just below the bottom of your squat. Test the height with an empty bar first.
• Bench press: Set the arms just below your chest at full arch, so you can lower a failed rep onto them.
• Deadlift: No arms needed. Pull on flat, stable flooring. Bumper plates help protect the floor if you drop a rep.

If you are shopping for a rack, compare frames in our best power racks roundup. Check what fits your uprights in the best spotter arms guide. If you are still choosing a style, squat rack vs power cage explains the difference in safety features.

Spotters and collars

A spotter adds a second layer of safety, especially on the bench press. Agree on signals before you lift. Always use collars on max attempts. A plate sliding off one side can tip the bar. Our best barbell collars guide covers the common types.

When to skip a max test

Skip a true max and use this calculator instead if any of these apply:

• You are new to the lift and your form still changes from set to set.
• You train alone with no safety arms, or your rack’s arms don’t reach your bench height.
• You are tired, sick, sore or coming back from an injury.
• You have a health condition, or a doctor has told you to avoid maximal efforts.

The Reynolds paper notes that age and existing medical conditions can make 1RM testing unsafe for some people. An estimate from a 5-rep set gets you most of the way with far less risk.

Accuracy limits: who the formulas don’t fit

A max rep calculator is only as good as the set you feed it and the people the formula was built on. Know the limits before you build a program on the number.

• Error is normal. Wikipedia’s summary of the research notes that estimates can differ from a tested max by 10% or more.
• Exercise matters. The deadlift ran low in every equation in the 1997 study. The squat was predicted well by only one.
• Study groups were narrow. Many of the source studies used college-aged lifters or new lifters. Very strong, very experienced or older lifters may not match.
• Rep speed and style matter. Paused reps, touch-and-go reps, belts and knee sleeves all change how many reps you get. Estimate with the same style you plan to test.
• Day-to-day changes are real. Sleep, food and stress move your performance. One set gives you one day’s estimate.

If an estimate and a real max disagree, trust the real max.

Common mistakes with a 1RM calculator

Most bad estimates come from the set, not the maths. These are the mistakes that skew the number most.

• Stopping far from failure. A set with 3 or 4 reps left gives a low estimate. The formulas assume you did as many reps as you could.
• Using high-rep sets. A set of 15 or 20 reps adds more error. Stay at 10 or fewer.
• Counting ugly reps. A bounced bench rep or a high squat should not count.
• Forgetting the bar. Enter the total weight, bar included. On a 45 lb bar with a 45 lb plate on each side, the total is 135 lb, not 90 lb.
• Mixing units. A 100 kg set entered as 100 lb gives an estimate less than half your real max. Check the unit toggle.
• Chasing the highest formula. Pick the average, not the biggest row. Planning from the top formula can set loads you can’t hit.

If loading math is where you slip, our guide to how much weight is 4 45 plates a side walks through the sums.

Using the calculator in kilograms

The calculator works the same in kg. Switch the unit toggle, and it converts the number already in the weight box.

In kg mode, the percentage chart rounds to the nearest 2.5 kg. That is the smallest jump most kg plate sets allow, using a 1.25 kg plate on each side. In lb mode, it rounds to the nearest 5 lb, which is a 2.5 lb plate on each side.

A few metric notes for UK and European lifters:

• Bars differ in weight, so check the one you own. Our Olympic barbell guide explains the common types.
• 1 kg equals 2.2046 lb. The calculator uses the exact factor (1 lb = 0.45359237 kg) when you switch.
• If your gym has only 2.5 kg plates as the smallest, your smallest jump is 5 kg. Fractional plates help fill the gap. See our best change plates guide.

Connecting your 1RM to other tools

Your 1RM feeds other calculations. The DOTS calculator scores your squat, bench and deadlift total against body weight, so you can compare lifters of different sizes. The home gym cost calculator prices the rack, bar and plates you need to train and test safely at home.

Home gym equipment for max training

Estimating a max needs only a bar and plates. Testing a true max at home calls for safety gear.

• A power rack or squat stand with safety arms. This is the key piece for squats and bench. See best power racks and best squat racks.
• A good bar. A standard bar with correct knurling and sleeve spin makes heavy singles feel stable. Our Olympic barbell guide covers what to look for.
• Bumper plates for pulls. They protect the floor and bar when a heavy deadlift comes down. Compare options in best bumper plates.
• Collars. Cheap and vital for heavy sets.
• A stable flat bench. Heavy bench singles need a bench that doesn’t wobble. See best flat weight bench.

Safety note

This page is general information, not coaching or medical advice. Max attempts put high loads on your joints and spine. Always warm up, use safety arms or a spotter for squats and bench press, and use collars. Stop if you feel sharp pain. If you have a health condition or an injury, or are new to lifting, talk to a doctor or qualified coach before testing a max. For most people training alone, an estimate is the lower-risk choice.