1RM Calculator

How It Works

This calculator uses three widely accepted formulas to estimate your one-rep max (1RM) from a submaximal effort:

• Epley — weight × (1 + reps/30). The most commonly used formula and the default in most training apps.
• Brzycki — weight × 36/(37 − reps). Tends to be more conservative, especially at higher rep ranges.
• Lander — weight × 100/(101.3 − 2.67 × reps). Falls between Epley and Brzycki for most inputs.

All three formulas lose accuracy above 10–12 reps. For the most reliable estimate, use a weight you can lift for 3–8 reps with good form.

Why It Matters

Knowing your 1RM lets you program training percentages accurately — the foundation of any structured strength program. SensAI uses these formulas (along with your recovery data) to auto-generate progressive training plans that adapt weekly.