1RM Calculator
Enter the weight and reps from a recent set to estimate your 1RM, compare formula range, and build a 50–100% load table.
Start with weight and reps
For a first pass, fill only the weight and reps fields, then calculate. Lift, formula, and rounding can stay on their defaults until you need more control.
Confidence: —
Formula spread: —
| Percent | Training load | Goal |
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| Formula | Estimate | Delta |
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- Bench press defaults to Mayhew, squat to O'Conner, and other lifts to a formula mean. If the range is wide or the set used high reps, use the lower side for training decisions.
- The calculator compares Epley, Brzycki, Lander, Lombardi, Mayhew, Wathan, and O'Conner equations. Research on submaximal prediction shows estimates tend to be more valid at lower repetition counts, but no equation can see your technique, fatigue, rest time, or injury history.
ready to use.
- Visible firstKeep the input and result positions clear.
- Results firstPut the main number up front and keep the process secondary.
- Less to askNo sign-up or extra information before using the tool.
Use a 1RM estimate to choose your next training loads
A one-rep max is the heaviest weight you could lift for one complete rep, but testing it directly can create fatigue and risk. This calculator turns a recent successful set into a practical planning number, then shows how that number changes across common 1RM formulas.
Start with the two fields that matter most: the weight you lifted and the reps you completed. Unit, lift, formula, and rounding can stay on their defaults for a quick estimate, or you can adjust them when you need a lift-specific recommendation, a different equation, or plate-friendly loading.
What the 1RM estimate means
The main result is an estimated one-rep max for training decisions, not a command to test a true max. Use it to set working weights, compare recent sets, or decide whether a planned heavy day still makes sense.
The result is strongest when the input set was recent, completed with full range of motion, and stopped before form broke down.
Use the right input set
Enter the actual weight lifted and the number of completed reps. The calculator accepts kg or lb, then keeps the result, formula range, comparison table, and training load table in the selected unit.
- Use a recent set completed with solid range and stable technique.
- Prefer about 3 to 5 clean reps for a practical 1RM estimate.
- Treat higher-rep sets more conservatively because pacing and muscular endurance affect them more.
Lift, formula, and rounding controls
The lift setting changes the recommended formula. Bench press uses Mayhew, squat uses O’Conner, and other lift choices use the mean of the available formulas.
The formula menu lets you view Epley, Brzycki, Lander, Lombardi, Mayhew, Wathan, O’Conner, or the formula mean. Rounding turns the estimate and percentage loads into practical jumps for the plates you normally use.
Calculate, Sample, Reset, and Copy
Use Calculate after entering your own weight and reps. Sample fills a ready-made example so you can see how the result, range, and tables behave before entering your set.
Reset clears the current values. Copy is for moving the result into a training log, note, or program without retyping the estimate and key table values.
How to read the recommendation
The recommended 1RM is the large planning number. The formula range shows how far the equations disagree, and the confidence note helps you judge whether the input set is close enough to a true strength set.
When the range is tight and the reps are low, the estimate is easier to use. When the range is wide, the set was high-rep, or the lift felt uneven, choose the lower side for training loads.
Using the training load table
The percentage table converts the estimated 1RM into 50% through 100% training loads. That makes it faster to choose warm-up jumps, back-off work, and heavier strength sets without doing the math again.
Use the top end for heavy singles and low-rep work, the middle ranges for most working sets, and the lower ranges for warm-ups, speed work, or lighter volume days.
Formula comparison example
For a bench press set of 225 lb × 5 reps, the Mayhew recommendation is about 267.8 lb. The formula range is about 253.1–267.8 lb, showing that different equations can produce meaningfully different answers from the same set.
If you use 5 lb jumps, a 90% heavy set from 267.8 lb lands near 240 lb. If the set was slower than usual or the range feels too wide, use the lower side rather than chasing the highest estimate.
Checklist and limits
- Check that the set used consistent technique and fully completed reps.
- Confirm the unit, lift selection, formula choice, and rounding before saving the result.
- Lower the training number if pain, fatigue, poor setup, or missing safeties change the session.
Research on submaximal bench press prediction, including PMID 12741856, reports better validity at lower repetition counts; references such as ExRx also present one-rep max prediction as an estimate from weight lifted and reps performed.
FAQ
What rep range gives the cleanest 1RM estimate?
Use a recent set you completed with solid form, ideally around 3 to 5 reps. Higher-rep sets can still be useful, but pacing and muscular endurance have a bigger effect, so treat a wide formula range as a signal to train from the lower side.
Why does bench press default to Mayhew?
The bench press setting uses Mayhew as the recommended formula because the calculator is tuned to show a lift-aware recommendation, not only a simple average. The comparison table still shows Epley, Brzycki, Lander, Lombardi, Mayhew, Wathan, and O’Conner so you can see the spread.
Why does squat default to O’Conner?
Squat uses O’Conner as the recommended formula. Other lift choices use the mean of the available formulas, which keeps the estimate neutral when the lift does not have a more specific default in this tool.
Does changing kg and lb convert my input?
Yes. When a weight is already entered, switching kg and lb converts that value and recalculates the visible estimate, range, comparison, and percentage table in the selected unit.
How should I use the 50–100% training load table?
Read the table as a planning shortcut. Use the top end for heavy singles and low-rep strength work, the middle ranges for most working sets, and the lower ranges for warm-ups, speed work, or lighter volume days.
Can I use the estimate to test a max today?
Use it as a planning estimate, not permission to attempt a true max. Before any heavy single, check warm-up quality, bar speed, pain, setup, spotters or safeties where needed, and whether today’s fatigue matches the number on screen.