How accurate is the One Rep Max Calculator for estimating my 1RM?

It’s usually close for 1–10 reps. Using the Average option can reduce bias across formulas.

Which formula should I pick in the One Rep Max Calculator?

Epley and Brzycki are popular for low-to-moderate reps. If unsure, choose Average of formulas.

Can the One Rep Max Calculator work with both kg and lb?

Yes. Select your unit in the form and the calculator shows results in both kg and lb.

What rep range gives the best results in the One Rep Max Calculator?

Sets of 1–10 reps provide the most reliable estimates with any included formula.

Does the One Rep Max Calculator provide training percentages?

Yes. It outputs suggested loads at common intensities like 60–95% of your 1RM.

Is the One Rep Max Calculator safe for beginners to use?

Yes. It estimates 1RM from submaximal sets, avoiding risky true max attempts.

Why do formulas in the One Rep Max Calculator give different numbers?

Each formula models strength endurance differently, so estimates vary slightly.

Can I round results in the One Rep Max Calculator to match my plates?

Yes. Choose a rounding step like 0.5 kg, 2.5 kg, 1 lb, or 5 lb for practical loading.

One Rep Max Calculator: Accurate 1RM Estimator

Use our One Rep Max Calculator to quickly estimate your true 1RM from any recent set. Enter the weight you lifted and the number of reps performed, select a formula, and get precise results in kilograms or pounds, plus practical loading guidance.

What is a One Rep Max (1RM)?

Your one rep max is the maximum amount of weight you can lift for a single repetition with proper form. Knowing your 1RM helps you set training loads, track progress, and program cycles for strength, power, and hypertrophy.

Testing a true 1RM can be demanding and risky if you are fatigued or new to lifting. That’s where a reliable estimator helps: by using submaximal sets and proven formulas, you can predict your 1RM safely and plan your training with confidence.

How to Use the One Rep Max Calculator

Enter the heaviest weight you lifted for a recent set.
Enter the number of reps completed with good form.
Select your unit (kg or lb) and an estimation formula.
Optionally choose a rounding step to match your plates.
Click Calculate 1RM to see your estimate and comparisons.

Which Formula Should You Choose?

Several peer-reviewed models exist. Each assumes a slightly different strength–endurance relationship. The calculator includes these popular options:

Epley: 1RM = weight × (1 + reps/30). A versatile choice for sets up to ~10 reps.
Brzycki: 1RM = weight × 36 / (37 ? reps). Often accurate for low to moderate reps.
Lombardi: 1RM = weight × reps^0.10. Simple power curve model.
Mayhew: 1RM = (100 × weight) / (52.2 + 41.9 × e^?0.055×reps).
O’Conner: 1RM = weight × (1 + 0.025 × reps). Easy and practical.
Wathan: 1RM = (100 × weight) / (48.8 + 53.8 × e^?0.075×reps).

Not sure what to pick? Choose Average of formulas to blend multiple models and reduce the bias of any single equation.

Accuracy Tips for Better Estimates

Use sets of 1–10 reps for best accuracy. Higher reps introduce more variance.
Record only clean reps with consistent technique and full range of motion.
Log the lift type (e.g., squat, bench, deadlift), grip, and tempo for future comparisons.
Use the same unit and rounding scheme each time to keep results consistent.
Retest after a training block; small strength gains won’t always match weekly fatigue.

How to Apply Your 1RM in Training

After you estimate 1RM, you can derive working weights from common intensity ranges:

Strength: 85–95% 1RM for low reps with longer rest.
Power: 60–80% 1RM moved fast with pristine technique.
Hypertrophy: 65–80% 1RM for moderate reps and controlled tempo.
Technique/Recovery: 50–60% 1RM for speed, skill, and blood flow.

Round your prescribed loads to the nearest plate increment you have available. The calculator’s rounding feature makes this easy by snapping estimates to steps like 0.5 kg, 2.5 kg, 1 lb, or 5 lb.

Safety and Practical Considerations

Warm up thoroughly before heavy work sets. If you’re new to training, prioritize form over load and avoid maximal attempts until you have a solid base. When in doubt, select the Average method and err slightly conservative—consistent progress beats testing bravado.

Finally, treat 1RM as a dynamic metric. Stress, sleep, nutrition, and skill all influence daily performance. Use this calculator regularly, but pair it with honest self-assessment to keep your programming both effective and safe.

One Rep Max Calculator