Free 1rm calculator
Find your one-rep max without testing it. Enter the weight you lifted and the reps you completed, and the calculator returns your estimated 1RM using the Epley formula — then use the percentage table to set training loads for any rep target, updated live, as you type.
On this page15 sections
Estimated 1RM should not replace actual testing with a spotter. Use percentage-based training as a guide only.
Results are estimates. Consult a professional.
What is a one-rep max (1RM)?
Your one-rep max — written 1RM — is the heaviest weight you can lift for a single, full repetition of an exercise with good form. It is the standard yardstick of maximal strength: when lifters say they squat 180 kg or deadlift 200 kg, they mean their 1RM. This one-rep max calculator estimates that single-rep number from a set you have actually done, so you never have to load a true max on the bar to find out where you stand.
It works for any barbell or machine lift — squat, deadlift, overhead press, row, leg press, curl. You enter the weight you lifted and the reps you completed, and the calculator predicts the one rep you could manage. This is the general 1RM tool; if you only care about the bench, the dedicated bench press calculator adds bodyweight strength standards on top of the same estimate.
How your 1RM is estimated: the Epley formula
This calculator estimates your one-rep max with the Epley formula, the most widely used 1RM prediction equation. It takes the two inputs you give it — the weight lifted and the reps completed — and projects the single rep you could manage.
The logic is simple: each rep beyond the first adds about 3.3% to the estimate (1 ÷ 30). A weight you can move for 5 reps is therefore roughly 1 + 5/30 ≈ 16.7% below your true single. Because Epley assumes a straight-line relationship between reps and load, it is most trustworthy in the range this calculator is built for — a hard set of about 2 to 10 reps. The formula itself is unit-agnostic; this calculator works in kilograms, so enter the load on the bar in kg.
How to use the one-rep max calculator
Getting an accurate estimate takes three steps and a single honest set:
- Pick a recent, hard set. Use a set you took close to failure — ideally 2 to 10 reps with clean, full-range form. A fresh set (not the last set of a long session) predicts best.
- Enter the weight and reps. Type the load on the bar and the reps you completed. The calculator applies the Epley formula and returns your estimated 1RM instantly.
- Use the number. Read it as your estimated single, then use the percentage table further down to set training loads for any rep target — without ever testing a true max.
A worked example using the one-rep max calculator
Alex just squatted 100 kg for 5 clean reps and wants to know the one-rep max without testing it. Here is exactly what the calculator does with that set.
Step 1 — Take the reps as a fraction of 30
Epley adds reps ÷ 30 to 1. With 5 reps that is 5 ÷ 30 = 0.1667, so the multiplier is 1.1667.
Step 2 — Multiply the weight by that figure
Multiply the load by the multiplier: 100 × 1.1667 = 116.7 kg. That is Alex's estimated one-rep max.
Step 3 — Sanity-check it against Brzycki
A second formula, Brzycki, reads a touch lower: 100 × 36 ÷ (37 − 5) = 3600 ÷ 32 = 112.5 kg. The two bracket the real number, which is what you would expect — more on the difference next.
Epley vs Brzycki: which 1RM formula is right?
Epley is not the only 1RM equation. The other heavyweight is Brzycki (1993), and the two are the most-cited, most-validated formulas in the gym. They take the same inputs but curve differently.
At a single rep both return the weight unchanged, and they agree closely at low reps. As reps climb they drift apart: Epley scales linearly and tends to read slightly higher, while Brzycki curves and stays a little more conservative. Brzycki also has a built-in limit — its denominator (37 − reps) collapses toward zero near 37 reps, so it is only meaningful in a normal training range.
| Reps performed | Epley estimate | Brzycki estimate |
|---|---|---|
| 3 | 110.0 kg | 105.9 kg |
| 5 | 116.7 kg | 112.5 kg |
| 8 | 126.7 kg | 124.1 kg |
| 10 | 133.3 kg | 133.3 kg |
Estimated 1RM from a 100 kg set at each rep count. Both formulas are most accurate in the 2–10 rep range; beyond it they diverge and overshoot.
Which is right? In practice the difference is small — usually a kilo or two — and research finds that no single equation wins for every lifter. This calculator uses Epley for its headline because it is the most common and the simplest to reason about; treat Brzycki as a useful second opinion, and the truth as the range between them.
Percentage of 1RM: the rep-max table
Once you know your 1RM, you can work out the weight to use for any rep target. The table below shows the percentage of your 1RM you can expect to lift for 1 to 10 reps. It is the inverse of the same Epley relationship the calculator uses, so it never contradicts your headline number — which is also why a single rep sits near 97% rather than a flat 100% in this scheme.
| Reps | % of 1RM | Example: 100 kg 1RM |
|---|---|---|
| 1 | 96.8% | 96.8 kg |
| 2 | 93.8% | 93.8 kg |
| 3 | 90.9% | 90.9 kg |
| 4 | 88.2% | 88.2 kg |
| 5 | 85.7% | 85.7 kg |
| 6 | 83.3% | 83.3 kg |
| 7 | 81.1% | 81.1 kg |
| 8 | 78.9% | 78.9 kg |
| 9 | 76.9% | 76.9 kg |
| 10 | 75.0% | 75.0 kg |
Percentages from the inverse Epley relationship (% = 100 / (1 + reps/30)). Individual rep capacity varies with the lift, training history, and how close to failure you go.
Read it both ways. To find a working weight, take your 1RM and multiply by the row you want — a 150 kg 1RM at the 5-rep row (85.7%) is about 129 kg for 5. To check an estimate, look up the reps you hit and divide the weight by the percentage. The percentages are a guide, not a law: a deadlift usually allows more reps at a given percentage than a bench, and a fresh lifter grinds out more than a fatigued one.
How to use your 1RM to program training
The real payoff of a 1RM is programming. Most serious strength plans are written as percentages — when a program says 5 × 5 at 80%, it means five sets of five reps at 80% of your one-rep max. Knowing your 1RM turns every such instruction into an actual number on the bar.
| Goal | % of 1RM | Typical reps | What it trains |
|---|---|---|---|
| Maximal strength | 85–95% | 1–5 | Top-end strength and neural drive |
| Power | 75–85% | 3–5 (explosive) | Force produced quickly |
| Hypertrophy | 65–80% | 6–12 | Muscle size, via volume and time under tension |
| Endurance | under 65% | 12+ | Muscular endurance and work capacity |
Common percentage bands. Ranges overlap by design — most well-rounded programs rotate through several across a training week or block.
A practical example: with a 100 kg squat 1RM, a strength day at 90% is 90 kg for triples, a hypertrophy day at 72% is about 72 kg for sets of 8, and a power day at 80% is 80 kg moved fast. As your estimated 1RM climbs, re-run the calculator and every working weight scales up with it — that is how a percentage-based program keeps loading you progressively without you guessing.
Why estimate your 1RM instead of testing it?
You could just keep adding weight until you fail at one rep — but estimating from a submaximal set is usually the smarter call, for three reasons.
- It is far safer. A true max attempt means grinding a single heavy rep where form breaks down first — exactly when injury risk is highest. A hard set of 5 stays well inside your control.
- It costs less recovery. Testing a real 1RM is taxing on the nervous system and can blunt the next few sessions. An estimate comes free from a set you were going to do anyway.
- It is repeatable. You can re-estimate from a normal working set every week or two and watch the trend, instead of building rare, draining max-out days into your plan.
The trade-off is precision: a tested 1RM is the ground truth, while an estimate is a prediction with a margin of error (roughly ±5% in the 2–10 rep range, widening fast above 10 reps). For programming, planning, and tracking progress, the estimate is more than accurate enough — most lifters never need to test a true max at all.
How to test a true 1RM safely
If you do want a real number — for a meet, a benchmark, or curiosity — test it deliberately, not on a whim. The estimate from this calculator is the perfect starting point: it tells you roughly where your max sits, so you can build up to it in sensible jumps instead of overshooting.
- Warm up thoroughly. Work up in steps — for example bar, then 50%, 70%, 85%, 92% — with low reps and full rest, so the heavy single is grooved, not a shock.
- Use a spotter or safety arms. Never test a max bench or squat alone. Set the rack pins or safety arms at a height that will catch a failed rep.
- Make small jumps near the top. Once you pass roughly 90% of your estimate, add weight in small increments (2.5–5 kg) and rest fully between attempts.
- Stop on form, not ego. If a rep slows to a crawl or your technique breaks, that attempt is your max for the day. Live to lift again.
Comparing 1RMs across lifters and lifts
A raw 1RM answers how much, but not how strong for your size. A 140 kg squat means something very different for a 60 kg lifter than for a 110 kg one. Two tools turn a 1RM into a fair, comparable score.
If you compete or train the three powerlifts, add your squat, bench, and deadlift 1RMs and run the total through the Wilks calculator, which scales your total by bodyweight and sex so lifters of different sizes compare on one scale. To gauge muscularity rather than strength, the FFMI calculator measures your fat-free mass index. And for a bench-specific estimate with strength standards built in, the bench press calculator is the focused companion to this general tool.
Data sources and methodology
This calculator's headline estimate uses the Epley formula (1RM = weight × (1 + reps/30)), the most widely used submaximal 1RM prediction equation. The comparison section and the worked example also reference the Brzycki formula (1RM = weight × 36 / (37 − reps)). Both are well-validated for low-rep sets and most accurate in the 2–10 rep range, where they typically fall within about ±5% of a tested max; accuracy degrades quickly above 10 reps and for explosive or isolation movements. The rep-max percentages are derived from the inverse Epley relationship so the table stays consistent with the headline.
Epley B. (1985) and Brzycki M. (1993), submaximal 1RM prediction equations.Frequently asked questions about the free 1rm calculator
About this one-rep max calculator
This one-rep max calculator runs entirely in your browser. The values you type never leave your device. It estimates your 1RM from a submaximal set with the Epley formula (1RM = weight × (1 + reps/30)), works for any lift, and updates instantly on every change.
Calculators Cloud offers 400+ free tools with no sign-up. The whole Health calculators shelf includes the bench press, Wilks, and FFMI tools alongside this one. Or browse the full calculator directory.