One Rep Max Calculator

Measuring your One Rep Max (1RM) is a crucial step in optimizing your strength training routine. Whether you’re a beginner or an experienced lifter, knowing your 1RM helps you tailor workouts to your exact capabilities, ensuring safer and more effective progress. Our One Rep Max Calculator provides a quick and scientifically backed estimate of your maximum lifting capacity based on the weight you lift and the number of repetitions performed.

What the One Rep Max Calculator Does

Our online calculator estimates your 1RM — the maximum amount of weight you can lift for a single repetition in exercises such as bench press, squat, deadlift, overhead press, and more. Instead of testing your true max (which can be risky or impractical), this tool uses your submaximal set (weight lifted and reps completed) to generate a reliable 1RM estimate and training loads.

How to Use the Calculator

1. Enter the weight you lifted during your set.
2. Input the number of repetitions you completed (best accuracy from 1–12 reps).
3. Select the exercise (e.g., bench press, squat).
4. Choose your weight unit (kilograms or pounds).
5. Click Calculate to see your estimated 1RM and training recommendations.

The calculator outputs:

• An estimated 1RM (rounded to the nearest unit).
• Percentage-based training loads (50% to 95% of 1RM).
• Rep ranges, sets, and rest guidelines for strength, power, hypertrophy, and muscular endurance.
• Each individual formula’s estimate for comparison.

How the Calculation Works

To improve accuracy across different rep ranges and lifter profiles, our calculator averages several validated 1RM prediction formulas. Each formula estimates 1RM from a given weight and rep count:

• Brzycki: 1RM ≈ weight × [36 ÷ (37 − reps)]
• Epley: 1RM ≈ weight × [1 + (reps ÷ 30)]
• Lander: 1RM ≈ weight × [100 ÷ (101.3 − 2.67123 × reps)]
• Lombardi: 1RM ≈ weight × (reps^0.10)
• Mayhew et al.: 1RM ≈ weight × [100 ÷ (52.2 + 41.9 × e^(−0.055 × reps))]
• O’Conner et al.: 1RM ≈ weight × [1 + (0.025 × reps)]
• Wathan: 1RM ≈ weight × [100 ÷ (48.8 + 53.8 × e^(−0.075 × reps))]

Final 1RM estimate = the average of all formula results.

Why average? No single formula fits every lifter, exercise, or rep range perfectly. Averaging reduces bias and stabilizes the estimate across most common scenarios.

Recommended input range: 1–12 reps. Accuracy drops as reps rise above ~12–15, especially with slow tempos or high fatigue.

Example: Step-by-Step 1RM Estimation

Suppose you benched 100 kg for 5 reps with solid form.

• Brzycki: 100 × [36 ÷ (37 − 5)] = 100 × (36 ÷ 32) = 112.5 kg
• Epley: 100 × [1 + (5 ÷ 30)] = 100 × 1.1667 ≈ 116.7 kg
• O’Conner: 100 × [1 + (0.025 × 5)] = 100 × 1.125 = 112.5 kg
• Lombardi: 100 × (5^0.10) ≈ 100 × 1.1747 ≈ 117.5 kg
• Lander: 100 × [100 ÷ (101.3 − 2.67123 × 5)] ≈ 100 × [100 ÷ 87.94] ≈ 113.8 kg
• Mayhew: 100 × [100 ÷ (52.2 + 41.9 × e^(−0.275))] ≈ 100 × [100 ÷ 84.0] ≈ 119.0 kg
• Wathan: 100 × [100 ÷ (48.8 + 53.8 × e^(−0.375))] ≈ 100 × [100 ÷ 85.8] ≈ 116.6 kg

Average ≈ (112.5 + 116.7 + 112.5 + 117.5 + 113.8 + 119.0 + 116.6) ÷ 7 ≈ 115.5 kg
Estimated 1RM ≈ 116 kg (rounded).

From here, loads for training zones are simple percentages. For example:

• 90% ≈ 0.90 × 116 ≈ 104 kg
• 75% ≈ 0.75 × 116 ≈ 87 kg

Round to your nearest plate increment (e.g., to the nearest 2.5 kg or 5 lb).

Training Zones and How to Use Them

Use your estimated 1RM to program intensity for different goals:

• Strength

  • 85–95% 1RM
  • 1–5 reps per set
  • 3–5 sets
  • 3–5 minutes rest

• Power (focus on bar speed; stop sets if speed drops)

  • 80–90% 1RM (for heavy strength-speed lifts)
  • 30–60% 1RM with explosive intent (for jumps/Olympic variations)
  • 1–3 reps
  • 3–5 sets
  • 3–5 minutes rest

• Hypertrophy

  • 65–80% 1RM
  • 6–12 reps
  • 3–4 sets
  • 60–90 seconds rest

• Muscular Endurance

  • 50–65% 1RM
  • 12–20+ reps
  • 2–3 sets
  • 30–60 seconds rest

Tip: Use the calculator’s percentage loads to plan sessions. For example, a 3×5 strength session at 85% of your 1RM, progressing 2–2.5% each week for 4–6 weeks.

Quick Reference: Typical % of 1RM by Reps

These are ballpark values; individual variation is normal.

• 1 rep ≈ 100%
• 2 reps ≈ 95–97%
• 3 reps ≈ 92–94%
• 4 reps ≈ 90–92%
• 5 reps ≈ 86–88%
• 6 reps ≈ 83–85%
• 8 reps ≈ 77–80%
• 10 reps ≈ 72–75%
• 12 reps ≈ 67–70%

RPE and Reps-In-Reserve (RIR): Autoregulate Your Training

Percentages are a great starting point, but daily readiness fluctuates. Layer RPE/RIR onto your percentages for safer, more productive training:

• RPE 10 = 0 RIR (max effort; no reps left)
• RPE 9 = 1 RIR
• RPE 8 = 2 RIR
• RPE 7 = 3 RIR

Practical use:

• Strength days (85–90%): aim for RPE 8–9
• Hypertrophy days (65–80%): aim for RPE 7–9
• Power emphasis: aim for RPE 6–8; stop before bar speed slows

If the prescribed percentage feels too heavy for the target RPE, reduce the load slightly; if it’s too light, add 1–2 small plate jumps.

Warm-Up and Testing Protocol (for Best Accuracy)

• General warm-up: 5–10 minutes light cardio + dynamic mobility for hips, shoulders, and thoracic spine.
• Specific warm-up:
  • 2×5 with the empty bar (focus on technique)
  • 5 reps @ ~40–50% of your estimated 1RM
  • 3 reps @ ~60%
  • 2 reps @ ~70%
  • 1–3 reps @ ~75–85% to produce your “test set” for the calculator
• Choose a load you can lift for 3–10 clean reps.
• Use consistent range of motion and tempo; avoid grinder reps that break form.
• Log weight, reps, and RPE for repeatability next time.

Plate Math and Practical Rounding

• Use the smallest plates available to match the calculator’s recommendation.
• Common gyms have 1.25 kg (2.5 lb) plates—use them to fine-tune intensity.
• When plate selection is limited, round down slightly for strength or power work; round up slightly for hypertrophy.
• Unit conversions: 1 kg = 2.20462 lb (multiply kg by 2.20462 to get lb; divide lb by 2.20462 to get kg).

Factors That Influence 1RM Estimates

• Exercise selection: Lower-body compound lifts (squat/deadlift) often translate better across reps than smaller single-joint movements.
• Tempo: Slow tempo and long eccentrics reduce reps at a given load, lowering estimates if not accounted for. Keep tempo consistent.
• Technique and range of motion: Partial reps or inconsistent technique distort estimates.
• Training age: Beginners can improve quickly; retest every 4–6 weeks. Advanced lifters may need smaller progressions.
• Fatigue, sleep, and nutrition: Poor recovery suppresses performance and may lower estimated 1RM on a given day.
• Equipment: Lifting shoes, belts, sleeves, and different bar types (stiff vs. whippy) can slightly affect results.

Programming Examples

• Strength Block (4 weeks, example for squat)

  • Week 1: 4×4 @ 80%
  • Week 2: 5×3 @ 85%
  • Week 3: 6×2 @ 90%
  • Week 4: 3×3 @ 80% (deload volume or intensity)
  • Retest 1RM estimate in Week 5

• Hypertrophy Block (4 weeks, example for bench press)

  • Week 1: 4×10 @ 70%
  • Week 2: 4×8 @ 72.5–75%
  • Week 3: 5×6–8 @ 75–77.5%
  • Week 4: 3×10 @ 65–70% (deload/intensity drop)
  • Retest with a 6–10 rep set

• Power Emphasis (for Olympic-lift derivatives)

  • 5–8 sets of 1–3 reps @ 60–80% with maximal speed
  • Full recovery between sets (2.5–4 minutes)

Interpreting Your Results

You’ll see:

• Estimated 1RM: Likely max weight for a single clean rep.
• Training Loads: Recommended weights at 50–95% of your 1RM for different training goals.
• Rep Ranges and Rest Periods: Strength (1–5 reps), Power (1–3), Hypertrophy (6–12), Endurance (12–20+).
• Individual Formula Results: Each formula’s estimate, so you can see the spread and consistency.

If the formulas diverge widely (e.g., a spread greater than ~10%), re-check your input reps, ensure consistent form, and consider retesting on a better-recovered day.

Common Mistakes to Avoid

• Testing after a hard session or on low sleep.
• Using inconsistent range of motion or bouncing reps.
• Overestimating reps by counting partials.
• Ignoring RPE/RIR and forcing grinders.
• Skipping warm-up sets.

Safety First

• Use a spotter or safety pins for heavy barbell work.
• Stop sets when your form breaks down.
• Avoid max testing if you’re injured, ill, or severely sleep-deprived.
• Warm up properly and don’t skip lighter ramp-up sets.
• Consult a qualified professional if you have medical concerns.

Frequently Asked Questions (FAQ)

Can I use this calculator for any exercise?

• Best for compound barbell lifts (bench, squat, deadlift, overhead press, row). It can estimate for machines and dumbbells but may be less precise due to stability differences and variable resistance profiles.

What if I can do more than 12 reps?

• Estimates become less reliable beyond ~12 reps. If you prefer higher reps, use a heavier load for 5–10 reps and recalculate.

Is it safe to test my true 1RM?

• Testing a true max can be risky without experience, a spotter, or proper equipment. The calculator provides a safer submaximal estimate.

How often should I recalculate my 1RM?

• Every 4–6 weeks works well for most. Advanced lifters may update more frequently using quality top sets (e.g., top set of 3–5 at RPE 8).

Should I use kg or lb?

• Either works. Be consistent, and round to your available plates.

Do upper and lower body lifts convert the same?

• Not always. Some athletes can do more reps at a given percentage on lower-body lifts. That’s one reason we average multiple formulas.

Does lifting tempo matter?

• Yes. Slower tempos reduce reps at a given load, potentially lowering your estimate. Keep tempo similar between tests.

What if my gym only has large plate jumps?

• Round conservatively and adjust with RPE/RIR. Add an extra set if the load feels too light to maintain training stimulus.

My individual results vary a lot between formulas—why?

• Formulas rely on different datasets and assumptions. Variation is normal. Averages reduce error, and retesting brings your estimate closer to true.

References

• Brzycki M. Strength testing—predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993.
• Epley B. Poundage chart. Boyd Epley Workout. 1985.
• Lander JE. Maximums based on reps. University of Nebraska. 1985.
• Mayhew JL, et al. Relationship of repetitions to predicted 1RM bench press performance in college football players. J Strength Cond Res. 1992.
• O’Conner B, Simmons J, O’Shea P. Weight Training Today. 1989.
• Wathan D. Load assignment. NSCA National Conference. 1994.

Take the Next Step: Calculate Your One Rep Max Now

Ready to optimize your training and unlock your full strength potential? Use our One Rep Max Calculator today. Enter your workout data and get a fast, reliable estimate of your 1RM with actionable training guidance tailored to your goals.

Start calculating now and take control of your fitness journey.

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