Calculator Inputs
Example Data Table
| Lift | Weight | Reps | RPE | Estimated Use |
|---|---|---|---|---|
| Bench Press | 100 kg | 5 | 10 | Strength block planning |
| Squat | 140 kg | 3 | 9 | Heavy weekly top set |
| Deadlift | 180 kg | 2 | 9.5 | Peaking cycle estimate |
| Overhead Press | 60 kg | 6 | 8 | Volume load planning |
Formula Used
This calculator compares seven common one rep max equations. RPE adjusts the rep count by estimated reps in reserve.
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
- Lombardi: 1RM = weight × reps0.10
- OConner: 1RM = weight × (1 + 0.025 × reps)
- Wathan: 1RM = 100 × weight ÷ (48.8 + 53.8 × e−0.075 × reps)
- Mayhew: 1RM = 100 × weight ÷ (52.2 + 41.9 × e−0.055 × reps)
- Lander: 1RM = 100 × weight ÷ (101.3 − 2.67123 × reps)
Best accuracy usually comes from hard sets of two to ten reps with consistent technique.
How To Use This Calculator
- Enter the weight lifted for your set.
- Select kg or lb.
- Enter the number of completed reps.
- Add RPE. Use 10 if the set reached failure.
- Choose a formula or use the average option.
- Set your goal percentage and training max percentage.
- Press calculate to view results above the form.
- Download the CSV or PDF for training records.
Why One Rep Max Matters
A one rep max shows the heaviest load you may lift once with sound form. It gives a clear strength benchmark. Lifters use it to plan warmups, working sets, deloads, and progress checks. Coaches also use it to compare strength across training blocks.
Testing a true max can be risky. It can strain joints and recovery. This calculator estimates max strength from a safer set. You enter a weight, completed reps, and effort level. The tool adjusts reps when the set was not taken to failure. Then it compares several popular equations.
Smart Planning With Percentages
Percentage training keeps workouts structured. Heavy singles may use ninety percent or more. Strength sets often sit between eighty and ninety percent. Hypertrophy work often uses sixty five to eighty percent. Speed or technique work may use lighter loads. These ranges are guides, not strict rules.
The training max option adds a safety buffer. Many programs use a conservative max near ninety percent of estimated capacity. This lowers missed reps. It also keeps technique cleaner. A conservative number is helpful after a break, during a cut, or when fatigue is high.
How To Use The Results
Start with the average estimate. Review the spread between formulas. A wide spread means the input set may be less reliable. Very high rep sets usually reduce accuracy. Sets of two to ten reps usually work better.
Use the percentage table for planning. Pick a target intensity. Match it to your goal and recovery. The chart helps show load changes across common training zones.
Always protect form. Stop a set when speed slows sharply. Do not chase numbers through pain. Use spotters, safeties, and proper equipment. Repeat the same lift style each time. This makes results easier to compare.
For best tracking, save the CSV or PDF after each test. Record sleep, body weight, and notes. Small context details explain big changes. Over time, these records show whether your program is building useful strength.
Update the estimate every four to six weeks. Test under similar conditions. Keep warmups steady. Compare the same formula first. Use averages only when decisions need overall training balance.
FAQs
What is a one rep max?
A one rep max is the heaviest weight you can lift once with proper form. It helps set training loads, measure progress, and compare strength over time.
Is an estimated max accurate?
It is an informed estimate, not a guaranteed true max. Accuracy improves when reps are low, effort is honest, and technique matches your normal lifting style.
Which formula should I choose?
The average option is useful for general planning. Use one formula consistently when tracking progress, because consistency often matters more than small formula differences.
Why does RPE change the result?
RPE estimates how many reps you had left. A set at RPE 8 may represent two extra possible reps, so the calculator adjusts effective reps.
What is a training max?
A training max is a conservative percentage of your estimated max. It helps reduce missed lifts and keeps your program easier to recover from.
Can beginners use this calculator?
Yes, but beginners should avoid true max attempts. Use controlled submaximal sets, focus on form, and keep conservative training loads.
Why is there a formula spread?
Each equation predicts strength differently. A larger spread means the estimate is less certain, especially after high rep sets or uneven effort.
Can I use pounds and kilograms?
Yes. Select your preferred unit before calculating. The calculator keeps the same unit throughout results, tables, exports, and chart values.