1RM Calculator
Training volume is the total workload in a session: sets multiplied by reps multiplied by weight. It is the primary driver of muscle growth and long-term strength development. Too little and the stimulus is insufficient. Too much and recovery becomes the limiting factor.
Intensity refers to how heavy you are lifting relative to your maximum, expressed as a percentage of your 1RM. The three main zones:
How close a set is to failure matters more than most realise. Tracking RPE or RIR accounts for daily variability in readiness and gives a more accurate read of your actual training stimulus than weight alone.
This protocol is designed to locate your true 1 rep max within 3-5 working attempts, using a structured warm-up and progressive load approach. Log each working set in the Calculator tab as you go.
- 1Warm up with a light load that easily allows 5-10 repetitions with full control and technique.
- 2Rest 1 minRecover fully before your next set.
- 3Select a load allowing 3-5 reps.Upper body: +4-9 kg or 5-10% Lower body: +14-18 kg or 10-20%
- 4Rest 2 min
- 5Select a conservative near-maximal load allowing 2-3 reps.Upper body: +5-10% Lower body: +10-20%
- 6Rest 2-4 min
- 7Load increaseUpper body: +5-10% Lower body: +10-20%
- 8Attempt your 1RM. Approach with full focus and execute with good technique.
- 9Successful lift: Return to step 6 and repeat with a heavier load.
Failed lift: Rest 2-4 min. Reduce load (upper: 2.5-5% lower: 5-10%) then return to step 8.
Enter your estimated 1RM above to see recommended warm-up loads.
This tool provides estimated values only. Calculations are based on submaximal lifting data and established research formulas. Actual 1RM can vary based on daily readiness, technique, fatigue, and individual physiology. Attempting sets of 5 reps or fewer with near-maximal loads carries significantly greater injury risk and should only be performed with appropriate supervision and proper technique in place. These estimates are for informational purposes and do not constitute professional training advice.
RPE and RIR Explained
A 1-10 scale rating how difficult a set felt, mapped to how many reps you had remaining. RPE 10 means zero reps left. RPE 8 means roughly 2 reps remaining. Adapted for strength training by Mike Tuchscherer of Reactive Training Systems.
A direct count of reps remaining when you stopped. RIR 0 means you could not have done one more. RIR 2 means two reps were remaining. Conversion: RPE = 10 minus RIR. So toggling between modes will automatically convert your entered values.
| RPE | RIR | Description |
|---|---|---|
| 10 | 0 | Maximum effort |
| 9.5 | 0 | Near max, no full rep left |
| 9 | 1 | One rep remaining |
| 8 | 2 | Two reps remaining |
| 7 | 3 | Three reps remaining |
| 6 | 4 | Four or more remaining |
Standard formulas assume you took a set close to failure. If you stopped with reps in reserve, the standard estimate understates your true 1RM. The RPE-adjusted formulas (RTS and Verro) correct for this.