1RM guide for real training sets
Turn a recent set into a usable training max
This 1RM calculator estimates a one-rep max from weight and reps, then turns that number into 50–100% training loads. It is meant for planning sets in the gym, not for proving that you should max out today.
What to read from the result
Recommended 1RM
The main number uses a lift-aware recommendation. Bench press starts from Mayhew, squat from O'Conner, and other lifts use the formula mean.
Formula range
The range shows how far the common equations disagree for the same set. A wide range means you should be more conservative.
Confidence cue
Three to five reps are usually the cleanest input range. Higher reps bring more pacing and endurance into the estimate.
Training loads
The table converts the estimate into percentages you can use for heavy work, volume work, and warm-up planning.
How to use the calculator
- Choose the lift and the unit. The English page starts with lb because many U.S. gym plates use pounds, but kg is still available.
- Enter a recent hard set: the weight on the bar and the number of completed reps. Keep reps between 1 and 12.
- Keep the recommended formula unless you already track one equation in your logbook. Choose a rounding step that matches your plates.
- Calculate, check the recommended 1RM and range, then use the training load table as a starting point for the next session.
How the estimate is calculated
The equations are estimates, not a rulebook
The tool calculates seven common 1RM equations. The formula itself is unit-neutral; the lb or kg choice only changes how the number is displayed and rounded.
For bench press, the recommended result uses Mayhew. For squat, it uses O'Conner. For deadlift, overhead press, row, and other lifts, it uses the mean so one equation does not dominate the result.
| Formula | Expression | Note |
|---|---|---|
| Epley | w × (1 + r ÷ 30) |
Often runs a little higher as reps rise, so it is useful for range checks. |
| Brzycki | w × 36 ÷ (37 − r) |
Often reads more conservatively for low-rep barbell sets. |
| Lander | 100 × w ÷ (101.3 − 2.67123 × r) |
A linear equation often seen in strength calculators. |
| Lombardi | w × r^0.10 |
Uses an exponent adjustment for repetition count. |
| Mayhew | 100 × w ÷ (52.2 + 41.9 × e^(−0.055r)) |
Useful as a comparison point around moderate rep ranges. |
| Wathan | 100 × w ÷ (48.8 + 53.8 × e^(−0.075r)) |
Best read as a barbell training estimate, not a promise. |
| O'Conner | w × (1 + 0.025r) |
A simple low-rep equation used as one more comparison. |
Example: 185 lb for 5 reps
How to apply that number
Heavy practice
90–95% sits near heavy singles or doubles. Use safeties and do not turn every session into a test.
Main strength work
80–85% is a practical zone for strength sets when technique is still solid.
Volume and speed
60–75% is better for volume, speed, or technique work when fatigue is already building.
Safety notes
Treat the estimate as a planning number
A calculated 1RM does not know your sleep, warm-up, technique, injury history, or whether a spotter is there. Use the result to set training loads, not to skip judgment.
- If pain or an injury history is involved, get qualified coaching or medical advice before heavy attempts.
- Use safeties and a spotter for lifts where a missed rep can pin you.
- Be conservative with 11+ rep inputs; they are affected more by endurance than max strength.
- Start a new block below the estimate and raise the load only when the bar speed and technique agree.
FAQ
Which formula should I choose?
Use the recommended option unless your training log already uses one formula. Consistency matters more than hunting for the highest number.
Does lb or kg change the formula?
No. The equations work the same way. The unit selector changes conversion, display, and rounding.
Why is the rep range capped at 12?
Above that, fatigue and endurance make the estimate less useful for a true max.
Can I attempt the calculated max right away?
Do not treat it as automatic permission. A real max attempt needs warm-up sets, setup, spotting, and a day when your body is ready.