What is 1RM?
1RM means one rep max: the heaviest weight you can lift once with good form. It is a useful strength benchmark for exercises like squat, bench press, deadlift, overhead press, rows, and weighted pull-ups.
Free lifting tool
1RM Calculator with RIR for kg and lb
Estimate your one rep max from the weight you lifted, the reps you completed, and how many reps you had in reserve. Use the result to choose smarter training weights without maxing out every workout.
Calculate your estimated 1RM
RIR defaults to 0 for a true max-effort set.
Estimated one rep max
116.5 kg
About 257 lb · based on 5 estimated reps to failure
Training percentages
90%
105 kg
85%
99 kg
80%
93.5 kg
75%
87.5 kg
70%
81.5 kg
65%
76 kg
How can it help?
Your estimated 1RM helps you set training percentages, track PRs, compare strength over time, and avoid guessing. For example, many strength plans prescribe working sets as 70–85% of your 1RM.
Why include RIR?
RIR means reps in reserve. A set of 100 kg for 8 reps at 0 RIR is all-out, while 100 kg for 8 reps at 2 RIR suggests you could have done about 10 reps. Including RIR makes the estimate more useful for normal training sets.
How to use this 1RM calculator
- Enter the weight you lifted.
- Choose kilograms or pounds.
- Enter the completed reps.
- Set RIR to 0 for an all-out set, or higher if you stopped early.
The estimate uses the Epley formula with RIR adjustment: completed reps plus RIR are treated as your estimated reps to failure. Use the result as a guide, not a medical or competition guarantee, and keep technique consistent when comparing sessions.
1RM calculator FAQ
What is a 1RM calculator?
A 1RM calculator estimates the maximum weight you could lift for one repetition based on a submaximal set. It helps lifters choose training loads without testing a true max every session.
How does RIR affect a one rep max estimate?
RIR means reps in reserve. If you complete 8 reps with 2 RIR, the calculator treats the effort like roughly 10 possible reps and adjusts the estimated 1RM upward.