1RM (one-rep max)
LiftShift shows 1RM estimates derived from your logged sets so you can track strength trends without testing maxes.
What a 1RM estimate means
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. In practice, testing a true 1RM is fatiguing, risky without a spotter, and impractical to do regularly across multiple exercises.
A 1RM estimate is a mathematically predicted value based on a submaximal set. For example, if you bench press 80 kg for 8 reps, LiftShift can estimate that your 1RM is around 99\u2013101 kg \u2014 without you ever needing to load that weight on the bar.
Example: You bench press 80 kg for 8 reps. Using the Epley formula, your estimated 1RM is 80 \u00d7 (1 + 8/30) = 80 \u00d7 1.267 = 101.3 kg.
LiftShift shows your highest 1RM estimate for each exercise, updated automatically after every workout. You can track how this estimate trends over time without ever testing a true max.
How LiftShift calculates 1RM
LiftShift uses the Epley formula, one of the most widely validated 1RM estimation equations:
1RM = weight \u00d7 (1 + reps / 30)
where weight is the load lifted and reps is the number of repetitions performed.
The formula is applied to every working set you log. LiftShift then takes the highest estimate across all sets for each exercise as your current estimated 1RM. Warm-up sets are excluded from 1RM calculation.
The Epley formula is most accurate for rep counts between 1 and 10. Estimates derived from sets with more than 10 reps tend to overestimate 1RM. LiftShift still calculates them but flags high-rep estimates with lower confidence.
Practical uses
- Track strength trends \u2014 Watch how your estimated 1RM trends upward (or downward) over weeks and months without ever testing a true max.
- Program design \u2014 Use your estimated 1RM to set percentage-based training loads (e.g. 75% of 1RM for hypertrophy work).
- Compare across rep ranges \u2014 A set of 100 kg \u00d7 5 reps and a set of 85 kg \u00d7 10 reps might produce similar 1RM estimates, helping you compare performances at different rep ranges.
- Spot discrepancies \u2014 If your estimated 1RM jumps sharply from one workout to the next, it may indicate you pushed harder that session or that your previous estimates were sandbagged.
Limitations
- The Epley formula assumes reps are performed to or near failure. If you leave several reps in reserve, the estimate will underestimate your true 1RM.
- Accuracy degrades above 10 reps. A 20-rep set will produce an unrealistically high estimate.
- Exercise-specific differences matter. The formula was validated on compound barbell lifts (squat, bench press, deadlift). Estimates for isolation exercises, machine movements, or bodyweight exercises are less reliable.
- An estimate is not a measurement. Your true 1RM on any given day depends on fatigue, nutrition, sleep, and mental readiness \u2014 none of which LiftShift can see.
- LiftShift shows the highest estimate across your history, not the highest actual lift. These are different concepts.
Safety note
Do not attempt a true 1RM based solely on LiftShift\u2019s estimate. The estimate is a mathematical projection, not a guarantee of capability. Attempting a maximal lift without proper preparation, warm-up, spotting, and technique can result in serious injury. If you want to test your true 1RM, use a structured peaking protocol, have a competent spotter, and prioritise safety over numbers.