Formula roots
Epley and Brzycki grew out of 1980s football weight rooms to scale training sets back to a predicted max without maxing out.
Gym origins
1RM Calculator — Epley, Brzycki, Lombardi
Inputs & Actions
Enter weight and reps to begin.
Results
Epley
—
1RM = W × (1 + R/30)
Brzycki
—
1RM = W ÷ (1.0278 − 0.0278R)
Lombardi
—
1RM = W × R^0.10
Working 1RM avg
—
Tip: Best accuracy usually comes from well-executed sets in the 2–10 rep range.
%1RM Load Table
Loads below are based on Working 1RM. Click “Use average” or any result to set it. Update reps/weight and recalc anytime.
| % of 1RM | Typical Reps | Load (kg) |
|---|---|---|
| These are guidelines; actual reps vary by lift, tempo, rest, and training status. | ||
How the 1RM formulas work
Epley
1RM = Weight × (1 + Reps/30)
Brzycki
1RM = Weight ÷ (1.0278 − 0.0278 × Reps)
Lombardi
1RM = Weight × Reps^0.10
Note: Treat estimates as starting points. Use a spotter and proper technique for heavy attempts.
How the 1RM formulas work
Note: Best accuracy is usually from well-executed sets in the 2–10 rep range.
5 Fun Facts about One-Rep Maxes
Curves beat straight lines
Strength isn’t linear with reps—that’s why Lombardi’s power curve (R^0.10) fits higher-rep sets better than divide-by formulas.
Curvy math
Fatigue swings
Being under-recovered can shave 5–10% off a session’s 1RM. Warmed-up but fresh sets give the best estimates.
Readiness
Lift-specific curves
Bench, squat, and deadlift can follow different fatigue curves—your bench 1RM predictor may not fit your deadlift.
Per-lift
Microloading helps
Tiny jumps (0.5–1 kg or 1–2 lb) keep progress moving when you’re near a ceiling; small plates beat stalls.
Tiny jumps
1RM Calculator – FAQ
Which 1RM formula should I use?
Epley and Brzycki are widely used and typically close in the 2–10 rep range. Lombardi uses a power curve and may differ more at higher reps.
How accurate are 1RM estimates?
They’re estimates. Results vary with rep range, lift selection, technique, fatigue, and training status. Treat them as starting points.
Can I enter weight in kg or lb?
Yes. The math is unit-agnostic—just be consistent for weight and results.
Is my data private?
Yes. All calculations run in your browser. No inputs are stored or uploaded.