How strong are you, really? If you have ever walked out of the gym after grinding out five reps with 225 pounds on the bench and wondered what you could have lifted for a single, all-out attempt, the Brzycki calculator is the tool that answers that question. It takes a weight you moved for several reps and converts it into an estimated one-rep max (1RM) using a regression equation developed by strength coach Matt Brzycki. This page explains the formula, shows how it compares to the popular Epley alternative, and turns the result into the 80%, 90%, and 95% training loads you can actually program next week for your bench press, back squat, or deadlift.
How to Use
- Enter the Weight Lifted — the total load on the barbell for the set you are evaluating, including the bar. Use a set that was challenging but technically clean.
- Set Reps Completed to the number of good, full-range repetitions you finished before the bar would not move again. Do not count partial reps or a grind that broke form.
- Pick the Exercise — Bench Press, Back Squat, Deadlift, or Overhead Press. The math is identical for every lift, but naming the movement helps you keep separate strength records.
- Choose your Units, pounds or kilograms. The formula is unit-agnostic, so the result simply carries whatever unit you entered.
- Read the result card. The highlighted Brzycki Estimated 1RM is your predicted single. Below it you will see the Epley estimate for comparison, the difference between the two, and the 80%, 90%, and 95% training loads derived from your Brzycki number.
A good input set is usually between two and ten reps at a moderate-to-hard effort. Very high rep counts (15+) are not strength estimates anymore — they are endurance, and the formula becomes unreliable there, which is why the rep field is capped at 36.
The Brzycki Formula
The Brzycki equation is one of several simple regression formulas that map sub-maximal repetition performance to a predicted maximum:
Brzycki 1RM = Weight × 36 ÷ (37 − Reps)
Where Weight is the load you lifted and Reps is the number of clean repetitions completed. The constant 36 and the (37 − reps) denominator were fitted to strength-training data and published in the early 1980s. As reps rise, the denominator shrinks and the predicted 1RM grows — reflecting the fact that a light weight lifted for many reps implies a larger maximum than the same weight lifted for one.
Worked example: 225 pounds for 5 reps gives 225 × 36 ÷ (37 − 5) = 8,100 ÷ 32 = 253.13 pounds. So a set of five with 225 predicts a one-rep max of roughly 253.
Brzycki vs Epley
The Epley formula is the other equation you will see on nearly every 1RM calculator:
Epley 1RM = Weight × (1 + Reps ÷ 30)
On the 225 × 5 example, Epley gives 225 × (1 + 5 ÷ 30) = 225 × 1.1667 = 262.50 pounds, about 9 pounds higher than Brzycki. The two formulas agree closely at low rep counts but diverge as reps climb: Brzycki is more conservative, predicting a smaller 1RM from higher-rep sets, while Epley trends slightly more optimistic. Most coaches treat the average of the two as a safe planning number, but this page reports Brzycki as the primary estimate because it is the more conservative (and therefore more injury-resistant) choice for programming.
Training Loads: What to Lift Next
An estimated 1RM is only useful if it converts into weights you can actually plan. Strength programs are built on percentages of your maximum:
- 80% load — the hypertrophy and muscle-building range. Sets of 6–10 reps live here.
- 90% load — the strength range. Heavy doubles and triples feel right at 90%.
- 95% load — the peaking range. Single-rep practice or a top set of one to two reps.
For a predicted 1RM of 253 pounds, that becomes about 202 pounds for hypertrophy work, 228 pounds for strength work, and 240 pounds for a peaking single. Plug in your own numbers and you have a ready-made week.
Examples
Example 1 — Bench press at 225 for 5 reps. A lifter completes five clean bench presses with 225 pounds. Brzycki predicts a 1RM of 253.13, Epley predicts 262.50, and the gap is about −9.38 pounds in Brzycki's favor. The 80% training load is 202.50, the 90% load is 227.81, and the 95% load is 240.47.
Example 2 — Back squat at 315 for 3 reps. A three-rep squat of 315 pounds yields Brzycki 1RM of 333.53 and Epley 346.50. The recommended strength load at 90% is 300.18, and a peaking single near 95% lands at 316.85 — just a few pounds above the set they actually did.
Example 3 — Deadlift at 275 for 2 reps. A double with 275 pounds predicts a Brzycki 1RM of 282.86. The 80% hypertrophy load works out to 226.29, a sensible starting weight for higher-rep deadlift assistance work.
Example 4 — Large-scale sanity check. Entering 1,000,000 pounds for 5 reps returns a Brzycki estimate of 1,125,000, confirming the engine scales to very large magnitudes without overflow.
FAQ
What is the Brzycki formula?
The Brzycki formula estimates your one-rep max from a sub-maximal set using the equation 1RM = Weight × 36 ÷ (37 − Reps), where Weight is the load you lifted and Reps is the number of clean repetitions completed.
How accurate is the Brzycki calculator?
It is an estimate, not a measured max. Research shows these regression formulas predict a true 1RM within roughly 5% to 10% for rep counts between one and ten, with accuracy declining as rep counts climb higher. Use it for planning, then test a real single periodically.
Is Brzycki better than Epley?
They are two fitted models of the same relationship. Brzycki is more conservative at higher rep counts and predicts a slightly smaller 1RM; Epley is marginally more optimistic. Choosing Brzycki means planning with the safer, lower number, which reduces the risk of jumping up in weight too fast.
What rep count gives the most reliable estimate?
Sets of two to five reps give the tightest estimates. A one-rep attempt needs no formula at all, while sets above ten reps start measuring muscular endurance rather than strength, and the prediction loses reliability.
Can I use Brzycki for bench, squat, and deadlift?
Yes. The formula is movement-agnostic, so the same equation works for the bench press, back squat, deadlift, overhead press, barbell rows, and similar compound lifts. Track each lift separately, because your 1RM will differ between them.
Should I train at the estimated 1RM itself?
No. The estimated 1RM is a reference point, not a working weight. Build your program around the percentage loads this calculator derives from it — typically 80% for hypertrophy, 90% for strength, and 95% for peaking singles.
Disclaimer
This Brzycki calculator is provided for informational purposes only and is not medical advice. Estimated one-rep max values are mathematical projections based on the inputs you enter and the Brzycki regression formula; they are not guaranteed measurements of your actual maximum strength. Lifting near your maximum carries a real risk of injury, especially when technique breaks down. Always warm up thoroughly, use competent spotters for the bench press, progress gradually, and consult a qualified coach, physical therapist, or physician before beginning or advancing a heavy resistance-training program.