Big 3 One Rep Max Calculator: Bench, Squat, Deadlift

This calculator estimates your one-rep max (1RM) for the three big powerlifting lifts: bench press, squat, and deadlift. You enter the weight you lifted and the number of repetitions performed, and it returns your estimated 1RM for each lift, along with a combined total. The calculation uses the Epley formula, a well-established method for estimating maximal strength from submaximal effort.

Formula

The calculator uses the Epley formula for each lift:

Estimated 1RM = Weight × (1 + Reps / 30)

Where:

• Weight is the load lifted (in kilograms or pounds – the formula is unit-agnostic).
• Reps is the number of repetitions performed to (or near) failure.
• Estimated 1RM is the predicted maximum weight you could lift for a single repetition.

The combined total is simply the sum of the three estimated 1RMs.

Worked Example

Using the default values:

1. Bench: 100 kg for 5 reps → 100 × (1 + 5/30) = 100 × 1.1667 = 116.7 kg
2. Squat: 140 kg for 5 reps → 140 × (1 + 5/30) = 140 × 1.1667 = 163.3 kg
3. Deadlift: 180 kg for 3 reps → 180 × (1 + 3/30) = 180 × 1.1 = 198.0 kg
4. Total: 116.7 + 163.3 + 198.0 = 478.0 kg

The calculator displays the same results, rounded to one decimal.

Why Estimate Your 1RM?

Testing a true one-rep max is mentally and physically taxing, and it carries a higher risk of injury than submaximal lifting. Estimating your 1RM from a set of 3–5 reps lets you:

• Set training loads as a percentage of your estimated max (e.g., 70% for volume work).
• Track strength progress without constantly peaking.
• Compare your total across the three lifts to see where you’re strongest and weakest.
• Plan competition attempts if you compete in powerlifting.

How to Choose the Right Weight and Reps

For the estimate to be reasonably accurate, the set should be challenging but not necessarily to absolute failure. The Epley formula works best when:

• You perform 1 to 10 reps (fewer than 10 is ideal).
• The weight is at least 70% of your true 1RM.
• You use good form and a consistent rep tempo.
• You are not fatigued from prior sets – use a fresh set for the best estimate.

If you use a very light weight for high reps (e.g., 20 reps), the formula will overestimate your max. For sets above 10 reps, other formulas (like the Lombardi) are more appropriate.

Common Mistakes and Misconceptions

• Using a set with poor form: If you cheat the reps, the estimate is meaningless.
• Mixing units: The formula is unit-agnostic, but you must be consistent. If you enter kilograms for bench and pounds for squat, the total will be wrong.
• Assuming the estimate is exact: The formula gives an approximation, not a guarantee. Individual variation can be ±5% or more.
• Thinking the total is a competition total: In powerlifting, the total is the sum of your best successful lifts in a single meet, which may differ from your estimated 1RMs.

Limitations of the Epley Formula

The Epley formula was developed from data on experienced lifters performing moderate-rep sets. It tends to:

• Overestimate 1RM for beginners who lack technique.
• Underestimate 1RM for very low-rep sets (1–2 reps) because the formula assumes a linear relationship.
• Be less accurate for high-rep sets (>10) as muscular endurance becomes a factor.

For most lifters training in the 3–8 rep range, however, it is a reliable and widely used predictor.

Alternatives to the Epley Formula

Several other 1RM estimation formulas exist, each with slightly different predictions:

• Brzycki: Weight × (36 / (37 − Reps)) – more conservative for high reps.
• Lombardi: Weight × Reps^0.10 – better for high reps.
• O’Conner: Weight × (1 + 0.025 × Reps) – similar to Epley but with a smaller coefficient.

The Epley formula is chosen here because it is simple, widely cited, and accurate in the typical powerlifting rep range (1–10).

Safety and Accuracy Notes

Estimating a 1RM is safer than testing a true max, but you should still take precautions:

• Always warm up thoroughly before attempting heavy sets.
• Use a spotter or safety pins when benching and squatting.
• Do not attempt a weight you cannot control with good form.
• If you are new to lifting, work with a qualified coach to learn proper technique.
• Remember that the estimated 1RM is a guide, not a prescription. Start with lighter loads when using it to program training.

Frequently Asked Questions

Is the Epley formula accurate for beginners?

It can overestimate for beginners because their technique and neuromuscular efficiency are not yet developed. As you gain experience, the estimate becomes more reliable.

Can I use this calculator for other lifts like overhead press or barbell row?

Yes, the formula works for any upper or lower body lift, but it is most commonly applied to the big three. For smaller muscle groups, the estimate may be less accurate.

What if I only know my 5-rep max?

That’s perfect – the Epley formula is designed for exactly that. Enter the weight and 5 reps, and you’ll get your estimated 1RM.

Should I train to failure to get the best estimate?

No, you don’t need to go to absolute failure. A set where you have 1–2 reps in reserve is sufficient and safer. The formula assumes you are near failure, but not necessarily at it.

How often should I recalculate my estimated 1RM?

Every 4–6 weeks is reasonable, or whenever your working weights increase significantly. Re-estimating too often can lead to unnecessary load changes.

Does the calculator account for body weight or age?

No, it only uses the weight and reps. For comparative purposes, you might look at strength-to-bodyweight ratios, but that is beyond the scope of this calculator.

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in bench_w | Bench weight | kg | 100 | 0
in bench_r | Bench reps | - | 5 | 1
in squat_w | Squat weight | kg | 140 | 0
in squat_r | Squat reps | - | 5 | 1
in dead_w | Deadlift weight | kg | 180 | 0
in dead_r | Deadlift reps | - | 3 | 1
out bench_1rm | Bench 1RM | kg | bench_w * (1 + bench_r / 30) | 1
out squat_1rm | Squat 1RM | kg | squat_w * (1 + squat_r / 30) | 1
out dead_1rm | Deadlift 1RM | kg | dead_w * (1 + dead_r / 30) | 1
out total | Big 3 Total | kg | bench_1rm + squat_1rm + dead_1rm | 1