One Rep Max Calculator
Estimate your one-rep max from weight and reps
Estimated one-rep max
Epley
Brzycki
Percentage of 1RM (Epley)
| % of 1RM | Weight | Plate-rounded |
|---|
What the Calculator Estimates
Your one-rep max, or 1RM, is the heaviest weight you can move for a single clean repetition of an exercise. It is the reference point behind percentage-based programs, which prescribe daily loads such as 80% of 1RM. Testing a true max is fatiguing and carries injury risk, so lifters often estimate it from a heavier set stopped short of failure. This tool turns a working weight and rep count into that estimate, shows two formulas side by side, and builds a percentage table for programming.
The Two Formulas
The page uses two well-known estimators, both written so a single rep passes the lifted weight straight through:
- Epley:
1RM = weight × (1 + reps / 30) - Brzycki:
1RM = weight × 36 / (37 − reps)
Epley tends to read slightly higher as reps rise; Brzycki is usually a touch more conservative. Seeing both is more honest than showing a single black-box figure, because the gap between them tells you how much the estimate is stretching.
Worked Example: 100 kg for 5 Reps
Enter 100 kg and 5 reps.
- Epley:
100 × (1 + 5/30) = 116.7 kg - Brzycki:
100 × 36 / (37 − 5) = 112.5 kg
The percentage table follows the Epley figure, 116.7 kg, and rounds each row to the nearest 2.5 kg:
| Percent | Exact | Plate-rounded |
|---|---|---|
| 100% | 116.7 kg | 117.5 kg |
| 90% | 105.0 kg | 105.0 kg |
| 80% | 93.3 kg | 92.5 kg |
| 75% | 87.5 kg | 87.5 kg |
| 70% | 81.7 kg | 82.5 kg |
| 60% | 70.0 kg | 70.0 kg |
| 55% | 64.2 kg | 65.0 kg |
In imperial the same math runs on pounds and rounds to 5 lb steps, and the unit toggle converts your entered weight rather than re-deriving it, so switch units before reading the table.
Reading the Table for Programming
The table spans 100% down to 55% in 5% steps, which covers the intensities most strength programs use. A few common anchors:
- 85–90% for heavy singles, doubles, and triples.
- 75–85% for classic 5×5 or 5/3/1-style main work.
- 65–75% for higher-volume hypertrophy work.
- 55–65% for speed work, technique practice, and warm-up ramps.
Use the plate-rounded column to set the bar and the exact column to track progress precisely over weeks.
Accuracy and Safe Use
The estimate is only as good as the set behind it. A hard 3-to-5 rep effort usually predicts a true max within a few percent, while sets above 6 reps grow progressively less reliable because technique, breathing, and pain tolerance start to matter as much as strength. Different exercises do not share one multiplier, so a bench-press estimate should not be used to set squat loads.
This tool is an educational training aid, not medical advice, and it cannot account for your injury history, mobility, or experience. Treat the output as a planning number, adjust it against how the bar actually feels, and never attempt a true maximal lift alone. For a fuller strength picture, pair it with body-weight and body-composition context.
The safest way to use the tool is to feed it a set you already perform in training. Warm up thoroughly, work up to a weight you can lift for a clean but challenging set of 3 to 5 reps, and stop while your form is still solid. That set is the input. A rep left in the tank gives a slightly conservative estimate, which is usually preferable to a grind where technique falls apart.
If your program is percentage-based, round the prescriptive load to something the bar can hold and adjust from there. A planned 80% session off a 116.7 kg estimate becomes 92.5 kg after plate rounding, and honest feedback on that set tells you more about your real strength than the formula alone. Retest every four to eight weeks, or after a deload or a change in body weight, and compare the new estimate with the old to see the trend. Remember that a single hard set is a sample, not a measurement, so treat a jump of one or two kilograms as noise rather than proof of progress.
A Second Example in Pounds
The unit toggle is easy to overlook, but it matters for the table. Suppose you enter 225 lb for 3 reps with pounds selected. Epley gives 225 × (1 + 3/30) = 247.5 lb, and Brzycki gives 225 × 36 / 34 = 238.2 lb. The table follows Epley and rounds to 5 lb steps, so 90% shows 222.8 lb exactly and 225.0 lb rounded, while 75% shows 185.6 lb exact and 185.0 lb rounded. Switching to kilograms would convert the entered weight rather than reinterpret the number, so set your unit first and then type.
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Frequently Asked Questions
Which estimate should I use to plan training — Epley or Brzycki?
Both are established and usually land within a few percent of each other below about eight reps. Many coaches split the difference or track whichever matches how a lifter actually performs. At 100 kg for 5 reps Epley gives 116.7 kg and Brzycki gives 112.5 kg, so the choice changes a working load by around 4 kg.
Why is the percentage table built from Epley rather than the average?
The tool uses the Epley value as its primary estimate when it draws the 100% to 55% table, so every percentage row is a fraction of 116.7 kg in the example above, not of the Brzycki figure. If your gym experience tracks closer to Brzycki, treat the table as a high estimate and adjust down.
Can I estimate a one-rep max from a set of 20 reps?
No. Input is capped at 12 reps, because beyond that a set measures endurance more than maximal strength and the formulas drift badly. If you can do more than 12 reps, add weight until the set falls inside the 1-to-12 range and enter that.
Do the same formulas work for squat, bench press, and deadlift?
No, not equally. The equations were fitted to average behavior and ignore differences in limb length, technique, and muscle fibre type, and they are less reliable on isolation exercises or movements where a set ends for reasons other than pure strength. Use a lift-specific estimate, not one number applied to every exercise.
What does the plate-rounded column mean?
It is the nearest weight you can actually load on a barbell, rounded to a 2.5 kg step in metric or a 5 lb step in imperial. The exact column is the precise percentage; the rounded column is what to put on the bar.
Is testing my true one-rep max safe?
A maximal attempt carries real risk of injury and should only be done with a spotter, safety pins, or both, after a thorough warm-up. This calculator is a training aid and not medical or coaching advice. Beginners and anyone with a health concern should use the estimate rather than a true max and consult a qualified professional.
Reviewed by the HandyTools Hub team · Last updated