This one rep max calculator estimates the heaviest weight you could lift once, from a set you have already completed. Enter the weight and the reps you got, and it returns your estimated 1RM from the Epley formula, a second opinion from Brzycki, and the full table of training percentages you would program from.
It works for any barbell lift. Most people use it as a bench max calculator, so there is a full bench press max chart below, but the same formulas apply to squat, deadlift, overhead press and their variations.
Knowing your 1RM matters even if you never test it, because nearly every serious strength programme prescribes working weights as percentages of maximum. Estimating from a set of 5 is safer than maxing out and accurate enough to program from.
How to Calculate or Determine 1 Rep Max
Every 1 rep max calculator takes the same two inputs, the weight lifted and the reps completed, and models how much strength you lose as reps go up. To determine 1 rep max from a set you have done, the two formulas in widest use, with weight w and reps r:
- Epley: 1RM = w × (1 + r/30)
- Brzycki: 1RM = w × 36 / (37 − r)
Worked from a set of 225 lb for 5 reps:
- Epley: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5 lb
- Brzycki: 225 × 36 / 32 = 253.1 lb
A detail most explanations get backwards: the two formulas do not agree at low reps and diverge as reps climb. They diverge most between 3 and 6 reps, by about 9 lb on a 225 lb set, and then converge. At exactly 10 reps they agree precisely, both returning 300 lb from 225 lb for 10. Above 10 reps Brzycki returns the higher number.
Both assume the set was taken to or very near failure. A comfortable set of 5 with three reps left in the tank is really a set of 8, and the estimate will come out low.
If you actually lifted a single, that is your one rep max. No formula needed, and the calculator returns the weight unchanged.
Bench Max Chart: Max Bench Press by Weight and Reps
Used as a max bench press calculator, the chart shows why reps matter more than lifters expect. Benching 225 for 3 and benching 225 for 8 are separated by nearly 40 pounds of estimated max, even though the bar weight is identical.
It also puts the classic milestone in context. If you can bench 225 lb, the two-plate bench, for 5 clean reps, your estimated max is about 262 lb. To get 225 as a single you need roughly 195 lb for 5.
For incline bench, apply the same formulas to your incline numbers, but do not convert between flat and incline. Most lifters incline somewhere around 70 to 80% of their flat bench and the ratio varies enough between individuals that estimating it is not worthwhile.
| Weight | 1 rep | 2 | 3 | 4 | 5 | 6 | 8 | 10 | 12 |
|---|---|---|---|---|---|---|---|---|---|
| 95 lb | 95 | 101 | 105 | 108 | 111 | 114 | 120 | 127 | 133 |
| 115 lb | 115 | 123 | 127 | 130 | 134 | 138 | 146 | 153 | 161 |
| 135 lb | 135 | 144 | 148 | 153 | 158 | 162 | 171 | 180 | 189 |
| 155 lb | 155 | 165 | 170 | 176 | 181 | 186 | 196 | 207 | 217 |
| 175 lb | 175 | 187 | 193 | 198 | 204 | 210 | 222 | 233 | 245 |
| 185 lb | 185 | 197 | 204 | 210 | 216 | 222 | 234 | 247 | 259 |
| 205 lb | 205 | 219 | 226 | 232 | 239 | 246 | 260 | 273 | 287 |
| 225 lb | 225 | 240 | 248 | 255 | 262 | 270 | 285 | 300 | 315 |
| 245 lb | 245 | 261 | 270 | 278 | 286 | 294 | 310 | 327 | 343 |
| 275 lb | 275 | 293 | 302 | 312 | 321 | 330 | 348 | 367 | 385 |
| 315 lb | 315 | 336 | 346 | 357 | 368 | 378 | 399 | 420 | 441 |
Read across from the weight you lifted to the reps you completed. Values are rounded to the nearest pound. The chart works identically in kilograms, because the formula scales linearly: 100 kg for 5 reps estimates a 117 kg max.
How the Seven Formulas Compare
No formula is correct in general. Accuracy depends on the lift, the rep range and the individual, and most estimates land within roughly 5% of a tested max when the set was 10 reps or fewer.
The practical way to read the spread: treat the lower estimate as your working max for programming and the higher one as an outside target. If Brzycki says 253 and Epley says 262, program from 253 and you will rarely miss a prescribed set.
Estimates run truest on the big compound barbell lifts and are less reliable on isolation work, where technique and stabiliser fatigue interfere more than raw strength.
| Formula | Estimate | Character |
|---|---|---|
| Brzycki | 253.1 lb | Most conservative at low reps |
| O'Conner | 253.1 lb | Simple linear, 2.5% per rep |
| Lander | 255.8 lb | Close to Brzycki |
| Wathan | 262.3 lb | Exponential, holds up across a wide rep range |
| Epley | 262.5 lb | The most widely used default |
| Lombardi | 264.3 lb | Power function, runs high |
| Mayhew | 267.8 lb | Exponential, the highest here |
A 15-pound spread from one set, about 6%. That spread is the honest error bar on any 1RM estimate, and it is why this calculator shows two formulas rather than presenting one as the answer.
Training Percentages of Your 1RM
This table is the reason to calculate a 1RM at all. Almost every strength programme prescribes work as a percentage of maximum, so the max is what turns "5 sets of 3 at 85%" into a real instruction.
The percentages read in the other direction too. If a programme calls for a set of 8, you are looking at roughly 80% of your max, which from a 300 lb bench is 240 lb.
Two practical rules. Recalculate every 4 to 8 weeks while you are progressing, because percentages from a stale max are the most common reason a programme starts feeling too easy in week six. And round working weights to the nearest 5 lb or 2.5 kg, since barbell maths beats false precision.
| % of 1RM | Reps typically possible | From a 300 lb max | Purpose |
|---|---|---|---|
| 100% | 1 | 300 lb | Max attempt |
| 95% | 2 | 285 lb | Heavy singles |
| 90% | 3 to 4 | 270 lb | Doubles and triples |
| 85% | 5 to 6 | 255 lb | Strength work |
| 80% | 7 to 8 | 240 lb | Strength and volume |
| 75% | 9 to 10 | 225 lb | Hypertrophy |
| 70% | 11 to 12 | 210 lb | Hypertrophy and volume |
| 65% | 13 to 15 | 195 lb | Muscular endurance |
| 60% | 16 or more | 180 lb | Warm-ups and technique |
Rep ranges are typical rather than fixed. Trained lifters usually get more reps at a given percentage than beginners, and the relationship is more consistent for squat and deadlift than for bench press.
Rep Max Conversions: 3RM, 5RM and 10RM
The same formulas run in reverse to convert between rep maxes, which helps when a programme prescribes a 3RM or 5RM test rather than a single.
Using Epley, the weight you can lift for a given number of reps is your 1RM divided by (1 + reps/30):
- A 3RM is about 91% of your 1RM
- A 5RM is about 86%
- An 8RM is about 79%
- A 10RM is exactly 75%
So a lifter with a 300 lb estimated max should expect roughly 273 lb for 3, 257 lb for 5 and 225 lb for 10.
To convert from one rep max to another, go through the 1RM. A 3RM of 250 lb implies a 1RM of about 275 lb, which implies a 10RM of about 206 lb. Chaining two estimates compounds the error, so treat the second number as a starting point to test rather than a target to trust.
How Accurate Are 1RM Estimates, and How Should You Test?
Accuracy depends almost entirely on the set you feed in:
- 2 to 5 reps: most accurate, typically within 2 to 3% of a tested max
- 6 to 10 reps: within roughly 5% for most lifters
- 11 to 15 reps: increasingly unreliable, because muscular endurance starts driving the result more than maximal strength
- A set stopped well short of failure: will underestimate, sometimes badly
If your tested max comes in below the estimate, the usual reason is not a bad formula. Grinding out a true single is a skill in itself, and lifters who rarely handle near-maximal weight tend to lag their estimates until they practise heavy singles.
If you do test a true max:
- Warm up thoroughly and build up in singles rather than jumping to the top weight
- Use a spotter and safety pins for bench and squat, always
- Test rarely. A few times a year is plenty, and estimates cover the gap
- Do not test on a day you are already fatigued, since a failed attempt costs more recovery than it returns in information
- Beginners should not test true maxes at all. Form breaks down under maximal load before the technique is there to protect the joints and spine, and an estimate serves the same programming purpose with none of the risk
Frequently Asked Questions
How do you calculate your one rep max?
To determine 1RM, take the weight and reps from a set close to failure and apply a formula. Epley is 1RM = weight × (1 + reps ÷ 30), so 225 lb for 5 reps estimates 262.5 lb. Brzycki is weight × 36 ÷ (37 − reps), which gives 253.1 lb from the same set.
How do I calculate my max bench press?
Use this as a max bench calculator by entering your bench numbers. Bench 185 lb for 5 reps and your estimated max is about 216 lb; 225 lb for 5 reps estimates about 262 lb. The bench max chart above covers weights from 95 to 315 lb across 1 to 12 reps, and works the same for incline bench if you use your incline numbers.
How many reps should I use to estimate my 1RM?
Between 2 and 5 reps gives the most accurate estimate, and up to 10 is still useful. Beyond 12 the set is limited more by conditioning than strength, so estimates drift. The set must also be taken to or near failure, or the result comes out low.
Which formula is more accurate, Epley or Brzycki?
Neither reliably. They diverge most between 3 and 6 reps, by about 9 lb on a 225 lb set, agree exactly at 10 reps, and cross over above that. Across seven common formulas the spread on one set is about 6%, so program from the lower estimate and treat the higher as an outside target.
What percentage of my 1RM should I train at?
It depends on the goal: 85 to 95% for maximal strength in sets of 2 to 6, 70 to 80% for hypertrophy in sets of 8 to 12, and 60 to 65% for warm-ups and technique. Recalculate every 4 to 8 weeks while progressing, since percentages from a stale max make a programme feel too easy.
Can I work out a 3 rep max or 10 rep max instead?
Yes. Using Epley, a 3RM is about 91% of your 1RM, a 5RM about 86%, an 8RM about 79% and a 10RM exactly 75%. From a 300 lb max that is roughly 273 lb for 3, 257 lb for 5 and 225 lb for 10.
Does the calculator work for squat and deadlift?
Yes, the formulas are lift-agnostic and tend to be slightly more consistent for squat and deadlift than for bench press. Do not convert between lifts, though. Ratios between bench, squat and deadlift vary far too much between individuals to estimate from one another.
Should I max out to find my one rep max?
Rarely, and not as routine training. A true max attempt is the most fatiguing and highest-risk set in the gym, and an estimate from a clean set of 3 to 5 is accurate enough to program from. If you do test, warm up in singles, use a spotter and safety pins, and pick a day you are fresh.