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SUPPS
Strength Tool

One-Rep Max
Calculator

Estimate your bench press, squat & deadlift 1RM using 3 scientific formulas. Get your training max, RPE map, and target strength goals.

Your Last Set

100 kg
kg
Enter the weight you lifted for a full set.
10 reps
Reps

Safety First

Never attempt a true 1-rep max without a spotter or safety bars. This calculator gives a safe estimate without the risk.

What is a One-Rep Max (1RM)?

Your One-Rep Max (1RM) is the gold standard for measuring absolute strength. It represents the maximum amount of weight you can lift for exactly one repetition with proper form. Whether you are a powerlifter working toward your squat max or a bodybuilder targeting your max bench press, knowing your 1RM is essential for programming effective training cycles.

Instead of risking injury by attempting a max lift every week, this one-rep max calculator lets you estimate your peak strength safely — based on a weight you can lift for 2–10 reps. This estimated value is also the basis for your training max (TM), the cornerstone of percentage-based programs like 5/3/1.

How to Use Your 1RM Results

Knowing your max strength isn't just for bragging rights. It's a critical tool for progressive overload. Most professional strength programs (like 5/3/1, Starting Strength, or Conjugate/Westside) use percentages of your 1RM to prescribe daily workout intensity.

  • Hypertrophy (Muscle Growth): 65–85% of 1RM · 6–12 reps · RPE 6–8
  • Pure Strength: 85–95% of 1RM · 1–5 reps · RPE 8–10
  • Power & Speed: 50–70% of 1RM · dynamic effort · max bar speed
  • Training Max (TM): 85–90% of estimated 1RM — used in 5/3/1 & conjugate programming
  • Endurance / Volume: Below 60% of 1RM · 15+ reps · RPE 5–6

Safety & Testing Tips

Attempting a true 1RM is physically and neurologically demanding. Always follow these safety guidelines:

  • Always use a qualified spotter, especially for bench press and back squats.
  • Ensure you are fully warmed up with 3–4 progressive warm-up sets.
  • Maintain strict form — a "max" that breaks form doesn't count and risks injury.
  • Don't test your true 1RM more than once every 8–12 weeks.
  • Use this 1RM calculator instead of testing frequently — it's safer and equally effective for programming.

The Science: 3 Formulas, One Accurate Answer

Most calculators use a single formula — this one averages three validated models for a more trustworthy estimate. Here's the science behind each:

1. The Epley Formula

Developed by Boyd Epley in 1985, this is the most common formula in gyms worldwide. It slightly overestimates for very high rep sets but is robust across the 2–10 rep range.
1RM = Weight × (1 + Reps / 30)

2. The Brzycki Formula

Created by Matt Brzycki, this formula is often considered more accurate in the 2–10 rep range and uses a geometric progression that matches real-world strength curves.
1RM = Weight × (36 / (37 − Reps))

3. The Lander Formula

Developed by J.R. Lander, this formula is particularly accurate for the 7–10 rep range, filling a gap where Epley and Brzycki can diverge. Including all three and averaging them produces a more reliable estimate across all rep ranges.
1RM = (100 × Weight) / (101.3 − 2.67123 × Reps)

Understanding RPE (Rate of Perceived Exertion)

The RPE column in the results table is a critical tool for intermediate and advanced lifters. RPE is a 1–10 scale measuring how hard a set felt relative to your maximum effort:

  • RPE 10: True max effort. No reps left in the tank. Equivalent to 100% of 1RM.
  • RPE 9: Could have done 1 more rep. Used for heavy singles/doubles in peaking blocks.
  • RPE 8: 2 reps remaining. The sweet spot for building strength without excessive fatigue.
  • RPE 7: 3 reps remaining. Common in volume phases and back-off sets.
  • RPE 6 or below: Light, technical work. Warm-ups or speed/technique sessions.

RPE-based programming — popularized by Mike Tuchscherer (RTS) and Barbell Medicine — lets you auto-regulate training intensity based on how you feel each day, rather than rigid percentages.

Fuel Your Strength Goals with the Right Supplements

To push your one-rep max higher, your nutrition and supplementation need to match your training intensity. These two products are specifically formulated for strength athletes:

Erotes Isolate Whey

25g grass fed whey protein isolate per scoop. Rapid absorption for muscle repair after heavy compound lifts.

Ares Pre-Workout

Clinically dosed caffeine, beta-alanine & citrulline for maximum power output on your heaviest sets.

Your 1RM is just one piece of the picture. Combine it with your caloric data for a complete performance plan:

TDEE Calculator

Calculate your Total Daily Energy Expenditure and maintenance calories to support your strength goals.

Body Fat Calculator

Measure your body fat percentage and lean body mass using the accurate U.S. Navy method.

Summary

Use this 1RM calculator as a compass for your training. By averaging three validated formulas — Epley, Brzycki, and Lander — you get a more trustworthy estimate than any single-formula calculator. Track your estimated max over time, use the RPE column to prescribe smart training loads, and let the percentage table guide your strength blocks. Consistency in the 75–90% range builds the foundation for a new personal best.