How to use
Enter the total weight, repetitions and RPE of a completed set. Then choose the repetitions and effort for a target set of the same lift. Calculate to see its estimated weight. The initial 100 kg × 5 reps at RPE 8 is a working example; replace it with your own set.
Optional equipment rounding rounds the total load down to a multiple of the selected step. A 2.5 kg step refers to the whole bar, not each side. Copy keeps a text record; this tool does not save workout history.
How this estimate works
Here RPE describes resistance-training effort through repetitions in reserve (RIR), not the general Borg exertion scale. RIR = 10 − RPE. Add RIR to completed reps to approximate repetitions to failure: n = reps + RIR.
Estimated 1RM = weight ÷ (1.0278 − 0.0278 × n). Target weight = estimated 1RM × (1.0278 − 0.0278 × target n). This combines an RIR estimate with Brzycki’s low-repetition equation. That combination is an assumption, not a validated prediction of your individual maximum. Half-point RPE uses the formula directly; no RTS percentage table or table interpolation is used.
Worked example
100 kg × 5 at RPE 8 gives 2 estimated reps left and n = 7. Estimated 1RM ≈ 120.02 kg. A target of 3 reps at RPE 9 gives n = 4 and ≈ 110.01 kg; a 2.5 kg increment rounds this down to 110 kg. Display rounding does not feed back into the calculation.
Kilograms to pounds: divide by 0.45359237; 100 kg ≈ 220.46 lb. Pounds to kilograms: multiply by 0.45359237; 100 lb = 45.359237 kg. Changing the unit converts the entered load.
Limits and corrections
Both sets must have 1–10 whole repetitions, RPE 7–10 in half-point steps, and reps + RIR no greater than 10. Lower-effort sets make RIR less precise. Load must be above zero and at most 1,000 kg; these are calculator limits, not safety thresholds.
RPE is subjective and estimates vary with experience, exercise, technique and fatigue. Use a set whose RPE you can judge; do not treat the answer as a training program, a bodyweight-exercise model or proof that a load is safe. Decimal point or comma is accepted, without thousands separators.
Frequently asked questions
Why do other RPE calculators disagree?
They may use a percentage chart, Epley or another model. This page identifies its equation so its results can be reproduced; differences do not establish which estimate matches you.
Why does the slider range change?
The two sliders in each set limit each other so reps + estimated reps left cannot exceed 10. Your selected values stay unchanged. A set of 9 reps at RPE 8 implies 11 reps to failure, outside this tool’s range. Recheck your entry or use a genuinely lower-repetition set; do not change RPE just to make it pass.
Does Clear change my units?
Clear removes entered values and results while preserving units and the equipment increment. Muted examples return in empty fields; they become confirmed output only after Calculate.