STRENGTH TOOLS
Strength Calculator
Estimate your max. Find the weight for your next set.
Find your one-rep max
Enter a recent set or a known 1RM.
Include the bar in your total weight.
Use a recent 1RM for this lift with the same technique and range of motion.
Example — enter your own numbers.
Maximum for one full rep.
Use a recent, well-rested set with consistent technique. You don’t need to test an actual maximum.
PERCENTAGE EXPLORER
What does this load mean?
Turn a percentage into weight and estimated reps.
View your percentage table
| % 1RM | Load | Max reps | Reps at 2 RIR |
|---|
“Max reps” means estimated capacity at 0 RIR, not a recommendation to train to failure. † Beyond 10 potential reps: less reliable. Above 15: no precise rep estimate.
WORKING-WEIGHT CALCULATOR
Plan your next set
Choose your reps and how many more you could do.
Total weight added across both sides of the bar.
The load may need to change between sets as fatigue builds. Match the intended effort while keeping your technique consistent.
What do RIR and RPE mean?
RIR = reps in reserve: how many more full repetitions you believe you could perform at the end of a set with the same technique. RPE is another way to describe that effort.
For example, 5 reps at 2 RIR means finish five reps feeling you could have completed roughly two more. Zero RIR means no further full rep available; you don’t need to attempt and fail another rep.
This calculator uses whole-number effort ratings from 0–4 RIR / RPE 6–10. Sets with more than 4 reps left are not suitable inputs for its 1RM estimate.
How should I use my result?
- Warm up progressively. Treat the suggested load as a starting point for your lift.
- Check the actual effort. If you have fewer reps left than intended, reduce the load. If you have more left, increase by a small available increment.
- Reassess each set. Sleep, recent training, rest periods and fatigue can change what a weight feels like. Update your estimate as your strength changes.
Use the same lift, equipment, range of motion and technique for the input set and planned set. These estimates are for standard strength lifts; they don’t transfer directly to Olympic lifts, weighted pull-ups or assisted exercises.
How are the estimates calculated?
We use the Brzycki equation and a practical RIR adjustment: potential reps = completed reps + reps in reserve. Adding RIR is a coaching approximation, not an individually validated strength test.
Target load = 1RM × (37 − target reps − RIR) ÷ 36
The percentage view uses the inverse of the same equation, so all three tools agree before display and equipment rounding. A single rep at 0 RIR returns the entered load as the 1RM.
Most useful at 10 potential reps or fewer. Results from 11–15 potential reps are rough extrapolations and are flagged. Beyond 15, precise estimates are withheld. These limits are software choices, not guarantees of accuracy within them.
Repetition capacity differs between lifters and exercises. This calculator uses a general model. Enter a separate set or known 1RM for each exercise you want to calculate. An estimated 1RM is a training reference, not a recommendation to attempt that weight.
For equipment rounding we round the working load down. The rounded weight may feel easier than the target. Percentages are calculated from unrounded values; displayed figures are simplified.
Background: Brzycki (1993) · Zourdos et al. (2016) · Nuzzo et al. (2024)