CALIBR Tools
One-rep max (1RM) calculator
Enter a set you have actually completed and this estimates your one-rep max, then shows the working loads that follow from it.
Estimated 1RM
116.5kg
Train from a training max of 105 kg — 90% of the estimate. Using the training max instead of a theoretical maximum keeps your working loads achievable on ordinary days.
| Reps | % of 1RM | Load (kg) |
|---|---|---|
| 1 | 100% | 116.5 |
| 2 | 95% | 111 |
| 3 | 92% | 107.5 |
| 5 | 87% | 101.5 |
| 8 | 80% | 93.5 |
| 10 | 75% | 87.5 |
| 12 | 70% | 81.5 |
How this is calculated
This uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). Every 1RM formula is an estimate, and all of them drift as rep counts climb — a set of 12 tells you far less about your true maximum than a set of three.
Treat the number as a programming anchor, not a personal best. If your set felt like it had three reps left in the tank, the estimate is low; if it was a genuine grinder, it is close.
Why 90%?
Hybrid athletes rarely turn up to a lifting session fully fresh. Programming from 90% of an estimated max builds in the headroom that running fatigue takes away, so a hard week does not turn every top set into a failed one.
Stop guessing the balance
CALIBR builds one adaptive plan across strength, running, recovery and fuelling — and recalibrates it as your training data comes in.
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