One rep max calculator — 1RM from reps and weight
Estimate your 1RM from any set with the Epley, Brzycki, Lombardi and O’Conner formulas, then read off training weights from 50 to 100 percent.
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220.5 lb — bar plus plates.
Count only clean reps taken close to failure. Two to five is the most accurate range.
Match this to the smallest plate pair you have, so the numbers are actually loadable.
Estimated maxes are for programming, not for bragging. Warm up properly, use a spotter or safety pins for anything heavy, and stop a set the moment form breaks down.
w × (1 + reps ÷ 30) — The most widely used. Gives the same result as Brzycki at 10 reps.
w × 36 ÷ (37 − reps) — A little lower than Epley below 10 reps and higher above; the basis of most percentage charts.
w × reps^0.10 — A power curve rather than a straight line; the flattest of the four.
w × (1 + 0.025 × reps) — A simple 2.5% per rep rule. Very close to Epley at low reps.
| % of 1RM | Weight | Approx. reps | Typical use |
|---|---|---|---|
| 100% | 115 kg | 1 | Max single — testing only |
| 95% | 110 kg | 3 | Heavy singles and doubles |
| 90% | 102.5 kg | 5 | Strength triples |
| 85% | 97.5 kg | 6 | Classic 5×5 / strength work |
| 80% | 92.5 kg | 8 | Strength–hypertrophy overlap |
| 75% | 85 kg | 10 | Hypertrophy, sets of 8–10 |
| 70% | 80 kg | 12 | Volume work, sets of 10–12 |
| 65% | 75 kg | 14 | Technique and back-off sets |
| 60% | 70 kg | 15 | Speed work and warm-ups |
| 55% | 62.5 kg | 17 | Deload / bar speed |
| 50% | 57.5 kg | 19 | Warm-up and rehab loading |
| Reps | Weight | % of 1RM |
|---|---|---|
| 1 RM | 115 kg | 100% |
| 2 RM | 112.5 kg | 97% |
| 3 RM | 107.5 kg | 94% |
| 4 RM | 105 kg | 92% |
| 5 RMyour set | 102.5 kg | 89% |
| 6 RM | 100 kg | 86% |
| 7 RM | 95 kg | 83% |
| 8 RM | 92.5 kg | 81% |
| 9 RM | 90 kg | 78% |
| 10 RM | 85 kg | 75% |
| 11 RM | 82.5 kg | 72% |
| 12 RM | 80 kg | 69% |
The formula, with your numbers
- Epley
- 100 × (1 + 5 ÷ 30) = 116.7 kg
- Brzycki
- 100 × 36 ÷ (37 − 5) = 112.5 kg
- Lombardi
- 100 × 5^0.10 = 117.5 kg
- O'Conner
- 100 × (1 + 0.025 × 5) = 112.5 kg
- Average
- (116.7 + 112.5 + 117.5 + 112.5) ÷ 4 = 114.8 kg
- Reps at a %
- reps ≈ 37 − 36 × (% of 1RM), the Brzycki equation rearranged
All four models are curve fits to real lifting data, not physics. They agree closely at low reps and diverge as reps climb, which is why the average is the safer number to programme from.
What this means
100 kg for 5 reps points to a one rep max of about 115 kg. The four formulas span 112.5 kg to 117.5 kg — a spread of 5 kg, which is the honest margin of error.
For programming, most strength work lives between 75 and 90 percent of that number: 85 to 102.5 kg for you. Hypertrophy work sits lower, around 65 to 80 percent, with more reps per set.
Re-estimate every four to six weeks from a hard set of three to five rather than testing a true single. You get the same information for a fraction of the fatigue and risk.
How to use the 1RM calculator
- Switch to kilograms or pounds — the toggle is remembered for next time.
- Enter the weight you lifted, including the bar.
- Enter how many clean reps you completed. Two to five reps taken close to failure gives the most accurate estimate.
- Set the rounding increment to match your smallest pair of plates, so every number in the percentage table is actually loadable.
- Read your estimated max, then work from the percentage table for programming.
The four formulas
| Formula | Equation | Behaviour |
|---|---|---|
| Epley (1985) | 1RM = w × (1 + r ÷ 30) | The most widely used. Linear, and reads high above about 8 reps |
| Brzycki (1993) | 1RM = w × 36 ÷ (37 − r) | Conservative at higher reps; the basis of most printed percentage charts |
| Lombardi (1989) | 1RM = w × r^0.10 | A power curve rather than a line; the flattest of the four |
| O'Conner (1989) | 1RM = w × (1 + 0.025 × r) | A simple 2.5% per rep rule; almost identical to Epley at low reps |
At three reps the four models typically fall within 2 percent of each other. At ten reps the spread can reach 8 percent. That is why this calculator shows all four and averages them rather than betting everything on one curve.
One quirk worth knowing: at a single rep, Epley and O'Conner do not return the input weight exactly (Epley gives 103.3 percent of it). Since a single is a one rep max, the calculator returns your entered weight for all four models when you enter one rep.
Reps to percentage of 1RM
This is the table most programmes are built on. The reps column is Brzycki's equation rearranged: reps ≈ 37 − 36 × (fraction of 1RM).
| % of 1RM | Approx. reps | What it is used for |
|---|---|---|
| 100% | 1 | Testing only |
| 95% | 2 | Heavy singles and doubles, peaking work |
| 90% | 4 | Strength triples |
| 85% | 6 | The classic 5×5 zone |
| 80% | 8 | Strength and hypertrophy overlap |
| 75% | 10 | Hypertrophy, sets of 8–10 |
| 70% | 12 | Volume work |
| 65% | 14 | Technique and back-off sets |
| 60% | 16 | Speed work and warm-ups |
| 50% | 19 | Warm-up and rehab loading |
Treat the rep column as an average, not a rule. Rep capacity at a given percentage varies a lot between people and between lifts — leg press and squat allow far more reps at 80 percent than a bench press does, and beginners generally manage fewer reps at a given percentage than experienced lifters.
Getting an accurate estimate
- Use a set taken close to failure. A set of 5 with 3 reps left in the tank under-estimates badly. Aim for 0 to 1 reps in reserve.
- Stay in the 2–5 rep range where you can. This is where all four models agree and where the physiology is closest to a true max.
- Count only clean reps. Grinding, bouncing or shifting technique inflates the rep count and therefore the estimate.
- Be consistent about conditions. Same equipment, similar time of day, similar warm-up, similar fatigue state. Comparing a fresh Monday set to a Friday set after squats tells you nothing.
- Estimate per lift. Your bench 1RM cannot be inferred from your deadlift, and the formulas behave differently across lifts.
How the estimate behaves across lifts
| Lift | How well rep-based estimates work |
|---|---|
| Back squat | Good. Large muscle mass, high rep capacity at a given percentage |
| Deadlift | Good at low reps; grip and lower-back fatigue make high-rep sets under-predict |
| Bench press | Tends to over-predict slightly — most people manage fewer reps at 85% than the chart says |
| Overhead press | Over-predicts. Small muscle mass and a short range of usable percentages |
| Olympic lifts | Unreliable. Snatch and clean and jerk are technique-limited, and multi-rep sets are rarely maximal |
| Machines and isolation | Rough at best. Rep capacity is very high and varies with the machine's strength curve |
Should you ever test a true max?
Competitive lifters do, because the competition demands it. Everyone else usually should not. Testing a genuine single needs a long warm-up, a spotter or safety pins, and costs days of recovery, and it carries the highest injury risk of anything in the gym. A hard set of three run through these formulas gives you a number accurate enough to programme from, and you can gather it from a session you were doing anyway.
Re-estimate every four to six weeks. Strength does not move fast enough to justify checking more often, and constant testing eats into the training that produces the progress.
Using the number safely
An estimated max is a planning tool. On any given day your actual capacity swings by 5 to 10 percent with sleep, food, stress and where you are in a training block. Autoregulate: if the prescribed weight moves badly, take some off. Warm up thoroughly, use collars, set the safety pins, and stop the set when form breaks rather than when the rep count says so.
Questions
How many reps give the most accurate estimate?
Sets of two to five taken close to failure are the sweet spot. Beyond about ten reps the estimate drifts high, because endurance and technique start to matter more than pure maximal strength.
Which 1RM formula is best?
They agree closely at low reps and give the same result at 10. Below 10 reps Brzycki reads slightly lower than Epley; above 10 it reads higher, and the gap grows quickly. Averaging them, as this calculator does, is a reasonable way to avoid betting on one model.
Does the same formula work for every lift?
Not equally well. Deadlifts and squats usually track the estimates closely; bench press often comes in a little under, and Olympic lifts are technique-limited enough that rep-based estimates are unreliable.
Should I actually test a true one rep max?
Rarely — it is fatiguing and carries more risk, especially without a spotter. A hard set of three, run through these formulas, gives you the number you need for programming most of the time.