One Rep Max Calculator

What Is a One Rep Max?

A one rep max is the most weight you can move through one full repetition before technique fails. It measures maximal strength at one instant, on one exercise, and it does not transfer between exercises: a 140 kg deadlift single says nothing precise about what you can press overhead.

The number matters because strength programs are almost never written in kilograms or pounds. They are written in percentages — five sets of three at 85 percent, a back-off set at 70 percent, an opener at 90 percent. Each of those instructions is inert until a maximum exists to take the percentage of, which is why lifters who have never attempted a maximal single still need a figure to program against.

There are two ways to get one. You can test it, warming up in steps and adding weight until a single fails, which gives the true answer for that day and costs a session, a spotter and some risk. Or you can estimate it from a set you have already completed, which costs one multiplication.

A Tested Max and an Estimated Max Are Different Numbers

An estimate is a prediction, and predictions carry error in a direction. Beia and colleagues, writing in Sports in 2024, compared seven repetition-based equations against measured maxima in 40 well-trained older adults with osteopenia or osteoporosis, mean age 73. All but one of the equations overestimated. Epley's, the one this page runs, came out 11.9 percent high on the leg press and 6.7 percent high on the lat pull-down, with standard deviations of 6.6 and 5.3 points.

That population and those machine exercises are not most people reading this, and the size of the error on a barbell bench press will not be the same. The direction is the part worth carrying away: a repetition-based estimate is more often a ceiling than a floor. If your result were 11.9 percent high, the true single behind an estimate of 262.5 lb would be 234.6 lb — a gap of 27.9 lb, arrived at without touching the bar.

So the figure is best read as the top of a plausible range rather than a weight to attempt. The percentages you take off it inherit the same optimism, which is why a prescribed 75 percent that feels like a hard triple is telling you the max above it was too generous.

Why Programs Are Written in Percentages of 1RM

MedlinePlus, the consumer service of the U.S. National Library of Medicine, advises adults to do strengthening activities two or more days per week and, for each exercise, to try repeating the movement 8 to 12 times, working up to 2 or 3 rounds.

Put that advice through the same equation this page runs and a rep range becomes a load range. A weight you can lift 8 times sits at 78.9 percent of the max Epley predicts from it, a weight you can lift 10 times at exactly 75.0 percent, and 12 times at 71.4 percent. General public guidance and a percentage-based program are describing the same territory in different units — roughly 71 to 79 percent of a maximal single.

This is also why the equation earns its place even if you never intend to attempt a single. The 1RM is an intermediate quantity: you feed it one set, it returns a maximum, and you immediately convert that maximum back into the weights that go on the bar.

1RM in the Bench Press, Squat and Deadlift

The Exercise Type dropdown offers Bench Press, Squat, Deadlift, Overhead Press and Other Exercise. It is a label rather than a variable. A set of 100 for 5 reps returns 116.7 on all five settings, because the exercise never enters the arithmetic — the choice is carried into the result so the figure you copy says which lift it belongs to.

Understanding that is more useful than complaining about it. Lifts genuinely do lose strength at different rates as reps accumulate; a deadlift set of ten and an overhead press set of ten are different physiological events, and no single divisor of 30 describes both. Epley's equation is a general-purpose approximation and treats them alike, which is the price of it fitting on one line.

If the bench press is the lift you care about, the bench-specific version of this tool runs the same equation with flat, incline and dumbbell variations and adds a bodyweight strength-standards table Bench Press Max Calculator.

How Do You Calculate Your One Rep Max?

One multiplication. Divide the rep count by 30, add one, multiply the weight you lifted by the result. Nothing else on the form takes part.

Estimated 1RM = weight lifted × (1 + reps ÷ 30)

The One Rep Max Formula, Written Out

The equation is Boyd Epley's, published as a poundage chart in 1985 while he was strength coach at the University of Nebraska; the 2024 comparison study cited at the foot of this page still lists that chart as its source. Read as a multiplier it is easier to hold in your head: dividing reps by 30 gives the fraction you add on top, so every rep is worth 3.33 percent of the weight you lifted.

Estimated 1RM = weight lifted × (1 + reps ÷ 30)

3 reps → × 1.1000     8 reps  → × 1.2667

5 reps → × 1.1667    10 reps  → × 1.3333

The answer is rounded to one decimal place at the very end and nothing is rounded on the way there, so any figure quoted on this page matches what appears on your screen. The arithmetic runs in your browser from a small formula module the page fetches when you press Calculate — which is a note about speed, not privacy, since this page carries analytics and advertising tags like every other page on the site.

Because the multiplier applies to the whole weight, the equation is unit-agnostic. Kilograms in, kilograms out; pounds in, pounds out. There is no unit selector and none is needed — but there is also no conversion, so a number typed from a pound scale returns pounds even if you were thinking in kilograms.

Step by Step

Three fields, and the panel opens empty: both number inputs start blank, so nothing is calculated until you press the button.

• Do a set to a clean technical limit and count the reps you actually completed. A rep ground out with a rounded back is not the kind of rep this equation was fitted to.
• Type the weight into Weight Lifted. It declares a minimum of 1 and accepts decimals — 102.5 for six reps returns 123.0.
• Type the rep count into Repetitions Completed. It declares a minimum of 1 and a maximum of 12.
• Choose the lift under Exercise Type. It opens on Bench Press and is recorded rather than calculated with.
• Press Calculate. Press Reset to clear both fields and return the panel to its empty state.

Two things about those declared bounds matter, because the form is submitted without browser validation. A rep count above the stated maximum still calculates — 200 for 20 reps returns 333.3, and for 25 reps returns 366.7 — and a fractional rep count goes through as well, with 0.5 reps at 100 returning 101.7. What is genuinely rejected is a weight or a rep count of zero or below, a non-numeric entry, or a field left blank: each of those raises the amber Check your inputs panel, reading Invalid input.

The tool does not recalculate as you type. On this page it runs only when you submit the form, so changing a value and reading the panel above it is a mistake the interface will not stop you making.

Worked Example: 80 kg for 8 Reps

A bench press set of eight at 80 kg, stopped at the point where a ninth would have needed help.

Estimated 1RM = 80 × (1 + 8 ÷ 30)

Estimated 1RM = 80 × 1.2667 = 101.3

Estimated 1RM

101.3

The readout leads with Estimated 1RM: 101.3, and the three rows beneath it repeat the weight, the reps and the lift you selected, so a copied result carries the inputs that produced it. Rounded to something you can load, that is a 100 kg single.

Notice how little the eighth rep was worth. The same 80 kg for seven reps returns 98.7 and for nine returns 104.0, so each rep either side of the count moves the estimate by 2.7 kg — small enough that a borderline rep you are not sure about is not worth arguing over, and large enough that habitually counting three extra is not survivable.

Worked Example: 225 lb for 5 Reps

Two plates a side on a 45 lb bar, five reps, in pounds this time.

Estimated 1RM = 225 × (1 + 5 ÷ 30)

Estimated 1RM = 225 × 1.1667 = 262.5

Estimated 1RM

262.5

Five is the rep count the research points to. Reynolds, Gordon and Robergs tested 70 adults aged 18 to 69 at 1, 5, 10 and 20 repetition maxima on the flat barbell bench press and the plate-loaded leg press, and found load fell non-linearly as reps rose. Building their own prediction equations from that data, they got the greatest accuracy from the 5RM set — an R-squared of 0.993 on the bench press and 0.974 on the leg press, against 0.955 and 0.915 from the 20RM.

Their conclusion reads as a limit rather than a preference: for the two lifts they tested, no more than 10 repetitions should be used in linear equations to estimate a maximum. The reps field here allows 12, two past that recommendation, and the chart below shows exactly what those last two reps do to the multiplier.

Why a True Single Comes Back Heavier Than You Lifted

Enter a genuine one-rep set and the calculator does not hand it back unchanged. A 140 kg single returns 144.7, because the multiplier at one rep is 1.0333 rather than 1.0000 — the equation adds 4.7 kg to a maximum you have already proved on the platform.

This is a property of Epley's equation, not a fault in the implementation. One plus one divided by 30 is 1.0333 whatever weight you feed it, so every result sits 3.3 percent above the lifted weight before the rep count does any work at all. Other published equations behave differently at one rep, and the Limits section below covers one that returns your weight exactly.

The practical rule follows from that. If you have actually tested a single, that tested figure is your 1RM and this page has nothing to add to it. Use the calculator for the sets you did not take to a maximum, which is most of them.

One Rep Max Chart: Multipliers for Every Rep Count

Every figure in this section comes out of the calculator itself. The middle column is the whole equation — find your rep count, multiply the weight you lifted, and you have the number the panel would give you. The right-hand column runs it backwards: it is the share of the estimated maximum that a set of that many reps represents.

The multiplier climbs in a straight line — each rep adds exactly 0.0333 — while the percentage column falls away in a curve. That mismatch is the entire argument about where the equation stops working: real strength does not decay linearly with repetitions, and the further right you read, the further the straight line drifts from what a body actually does.

One Rep Max Chart in Kilograms

Common barbell loads down the side, rep counts across the top. Find the row for what you lifted and read across to the set you did.

Two cells on the 100 kg row are worth comparing. Five reps predicts 116.7 and eight predicts 126.7 — a spread of 10.0 kg produced by three reps on an identical bar. Counting a set generously is not a rounding error, it is the difference between two training blocks.

One Rep Max Chart in Pounds

The same table again, built around the loads that come off a 45 lb bar with standard plates.

Nothing in the arithmetic changed between the two tables. A set of five gets multiplied by 1.1667 whether the number in front of it means kilograms or pounds; only the unit you were thinking in differs, and the calculator never learns which one that was.

Percentage of 1RM Training Chart

Having an estimate is only useful once it becomes a weight. This runs the 80 kg for 8 reps example — an estimated maximum of 101.3 — down the training percentages most programs ask for, with a loadable figure beside each.

Percentages here are taken from the unrounded maximum rather than from the 101.3 on screen, which is why the exact column can sit a tenth away from what you would get by multiplying the displayed figure. At these weights that gap never approaches a plate change, so round to whatever your gym actually stocks and let the decimal go.

How to Read Your Result

The figure predicts one thing: the heaviest single you could probably manage today, on the lift you just did, in the unit you typed. It is not a target to walk over and attempt, not a measure of how strong you are relative to anyone else, and not portable to another exercise.

What the Panel Shows

The large readout is the estimate — for a bench press set of eight at 80 kg it reads Estimated 1RM: 101.3. Three rows below it repeat the inputs, and they echo the raw values the form submitted: Weight Lifted 80, Reps Completed 8, and Exercise benchpress, spelled as the stored option value rather than the label on the dropdown. There is no gauge or colored band on this page, and deliberately so: a maximum has no good or bad zone, since 101.3 is a strong bench for one person and a warm-up for another.

Copy result puts the readout and those rows on your clipboard as plain text, which is the quickest way into a training log. Reset empties the two number fields, returns Exercise Type to Bench Press and puts the panel back to its starting state.

Turning the Estimate Into Training Weights

Treat the maximum as an input rather than an answer. Take the percentage your program asks for, apply it to the estimate, then round to something you can load. Working from the 225 lb example, whose estimate is 262.5, a five-by-five at 80 percent is 210.0 lb, a heavy triple at 90 percent is 236.3 lb, and a back-off set at 70 percent is 183.8 lb.

Rounded to the nearest 5 lb those become 210, 235 and 185 — never more than 1.3 lb from the exact figure, which is invisible against the day-to-day swing in what you can actually lift. Rounding is the point at which the decimal stops mattering, and it arrives faster than most people expect.

Two conversions from the chart above are worth keeping in your head as a check on all of this. A weight you can lift ten times is 75.0 percent of the estimated maximum, and one you can lift five times is 85.7 percent. If a session prescribes 75 percent and the bar moves like a hard set of three, the estimate that produced the number was too high.

Sanity Checks Before You Trust the Number

Three questions catch most bad estimates, and each takes a few seconds. None of them is caught by the form, because every one produces a perfectly well-formed number.

• Did the set genuinely end where you counted it? A set stopped four reps short of a technical limit loses four reps' worth of multiplier, which is 13.3 percent of the weight you lifted.
• Was the rep count honest in the other direction? Eight reps entered for a set that was really five moves a 100 kg estimate from 116.7 up to 126.7.
• Does the answer come back in the unit you meant? Type 100 while thinking in pounds and the 116.7 you get is pounds, because the tool converts nothing and asks nothing about units.

A fourth check applies only if you train in a rotation of variations. The estimate belongs to the exact movement you performed — a paused bench and a touch-and-go bench are not the same lift, and the calculator has no way to tell them apart.

Limits: When This Estimate Does Not Apply

Every repetition-based maximum is a curve fitted to a population and then applied to one person. Three situations make that fit poor enough to change what you should do with the number.

The Estimate Drifts as the Rep Count Rises

The multiplier grows without any ceiling, because a straight line has none. At fifteen reps it reaches 1.5000 and at thirty it reaches exactly 2.0000, so the equation will cheerfully claim that a set of thirty predicts double the weight on the bar — 100 kg for thirty reps returns 200.0. Nothing in the arithmetic knows that a set that long is measuring muscular endurance rather than maximal strength.

Reynolds and colleagues drew the line at ten repetitions for linear equations of this type, and the longest set they tested was twenty. Beyond that there is no measurement underneath the arithmetic at all — only the straight line, still climbing. Read a result from more than ten reps as a rough indication, and one from a set long enough to be conditioning work as no result at all; the field's declared maximum of 12 is a label, not a gate.

Why Another Calculator Gives You a Different Number

Epley's is one of several published equations and they disagree with each other. The 2024 comparison above ran seven of them side by side — Brzycki, Epley, Lander, Mayhew, O'Connor, Wathen and Kemmler. The one you are most likely to meet on another calculator is Brzycki's, which divides where Epley multiplies: the weight times 36, divided by 37 minus the reps.

Brzycki estimate = weight lifted × 36 ÷ (37 − reps)

Run both on 100 kg for five reps and Epley returns 116.7 against Brzycki's 112.5, a gap of 4.2 kg. At three reps the gap is 4.1 kg. At exactly ten reps the two agree to the decimal, both returning 133.3, and past that they cross: at twelve reps Brzycki gives 144.0 where Epley gives 140.0. Brzycki also returns your weight unchanged from a genuine single, which is the behavior the section above described.

This page runs Epley and only Epley — there is no formula selector. If you have been tracking a maximum from a calculator built on Brzycki, expect the figure here to sit a few percent higher at low rep counts, and do not mix results from the two in one training log.

Where the Number Should Not Be Used

Five uses the estimate cannot support, in rough order of how often they are attempted anyway.

• As a weight to attempt on the day. The estimate comes from a submaximal set, and the 2024 comparison above found equations of this family running high rather than low.
• On a lift you did not perform. The exercise selector changes nothing, so carrying an estimate from a squat set over to a bench press is arithmetic with no evidence underneath it.
• For technical or explosive lifts. Snatches, cleans and jerks break down on technique long before the muscles reach a limit, and a repetition curve has nothing to say about that.
• As a return-to-training benchmark after injury. That is a clinical judgment rather than an arithmetic one, and no equation on this page is qualified to make it.
• As a comparison between two people. A one rep max ignores bodyweight completely, which is the whole reason coefficient scores exist.

To put a total on a scale that survives a difference in bodyweight, run your best squat, bench press and deadlift through the Wilks Calculator.