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//// Health · Strength Training

One-Rep Max Calculator

Enter the weight and reps you just lifted to estimate your 1RM using three proven formulas — then use the percentage table to plan your training loads.

Where this fits

❤️ HealthHouseholds

This tool sits in the health domain and connects best with the next tools in that decision lane.

Healthy BMI18.5 – 24.9
Daily Calories2,000 – 2,500
Sleep Cycle90 min

Back Squat — Estimated 1RM

257.2

lbs (average of 3 formulas)

lbs

Formula Estimates

Epley262.5 lbs
Brzycki253.1 lbs
Lander255.8 lbs
Average (used)257.2 lbs

Training Percentage Table

50%128.6 lbs
60%154.3 lbs
65%167.2 lbs
70%180 lbs
75%192.9 lbs
80%205.8 lbs
85%218.6 lbs
90%231.5 lbs
95%244.3 lbs
100% (1RM)257.2 lbs
1

Epley formula (1985)

1RM = weight × (1 + reps / 30)

= 225 × (1 + 5 / 30) = 225 × 1.1667

= 262.5 lbs

Epley B, 1985 — World Powerlifting

2

Brzycki formula (1993)

1RM = weight × 36 / (37 − reps)

= 225 × 36 / (37 − 5) = 225 × 36 / 32 = 225 × 1.1250

= 253.1 lbs

Brzycki M, 1993 — Strength & Conditioning Journal

3

Lander formula (1985)

1RM = weight × 100 / (101.3 − 2.67123 × reps)

= 225 × 100 / (101.3 − 2.67123 × 5) = 225 × 100 / 87.9438

= 255.8 lbs

Lander JE, 1985 — Journal of Applied Sport Science Research

4

Average of all three formulas

avg = (Epley + Brzycki + Lander) / 3

= (262.5 + 253.1 + 255.8) / 3

= 257.2 lbs estimated 1RM

Key insight

Based on 225 lbs × 5 reps, your estimated 1RM is 257.2 lbs. Formulas are most accurate for 1–10 reps — accuracy drops above 10. Use for programming percentages, not max attempt selection.

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Formula Accuracy

All three formulas are most accurate in the 1–6 rep range. Beyond 10 reps, estimates diverge due to individual fatigue curves. Epley tends to overestimate; Brzycki is more conservative at higher rep counts. Use the average for programming and treat the result as an estimate, not a target for your next max attempt.

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