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
Want to estimate your one-rep max without attempting a risky single? This calculator uses well-known strength formulas to estimate your 1RM from a weight and rep count. It is a practical way to plan training, track progress, and choose working weights for exercises like squats, bench press, and deadlifts.
What 1RM means: your one-rep max is the heaviest load you can lift once with good technique. Because testing a true max can be fatiguing or unsafe, many lifters use submax sets and convert them into an estimated 1RM. The estimate is not perfect, but it is often accurate enough for programming.
This calculator applies multiple formulas (Epley, Brzycki, and Lombardi) and also provides an average, giving you a more balanced view. Each formula models the relationship between reps and load slightly differently, which is why results can vary by a few percent. The “Working 1RM” is a practical midpoint you can use for percent-based training.
How to use it:
- Select your weight unit and enter the load you lifted.
- Enter the number of reps you completed with solid form.
- Click Calculate to see the estimated 1RM results and the working average.
- Use the %1RM load table to find training weights for common rep ranges.
- Adjust the inputs to compare different sets or exercises.
Real-world uses: estimate max strength for a new training block, compare progress over time, or select weights for 5x5, 3x8, or a hypertrophy day. Coaches often use these estimates to keep lifters progressing without frequent max testing. It is also useful when you are returning after time off and want a safe starting point.
Tips for better accuracy: the best estimates usually come from well-executed sets in the 2–10 rep range. Very high reps can skew predictions, and poor form can inflate numbers. Always prioritize technique, and use a spotter or safety bars when lifting heavy.
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.