You’ve just crushed a set of squats. Eight reps at 100kg, and you’re wondering what my actual one-rep max is? You pull out your phone, search for a calculator, and suddenly, two different formulas are giving you two different answers.
Which one do you trust?
This is a question a lot of lifters never stop to think about. They just grab whatever number pops up first and move on. But if you’re serious about tracking gym progress, building strength properly, or running a percentage-based training program, knowing the difference between the Epley and Brzycki formulas actually matters.
Let’s break both down practically, clearly, and without the math headache.
What Is a 1RM and Why Does It Matter?
Your one-rep max (1RM) is the maximum weight you can lift for a single complete repetition with good form. It’s the gold standard of strength measurement.
Here’s the thing: most people never actually test their true 1RM. And honestly, they shouldn’t. Walking up to a barbell and maxing out every week is a fast track to injury. Instead, you do a submaximal set (say, 5 reps at a heavy weight) and use a formula to estimate where your max probably sits.
That’s where Epley and Brzycki come in. Both are 1RM calculator formulas designed to give you that estimate without the risk of a true max effort.
The Epley Formula: Simple and Widely Used
The Epley formula was developed by Boyd Epley in 1985. He was a strength coach at the University of Nebraska, and he needed a quick, practical way to estimate max strength for his athletes.
The formula looks like this:
1RM = Weight × (1 + Reps / 30)
So if you lifted 100kg for 8 reps:
1RM = 100 × (1 + 8/30) = 100 × 1.267 = 126.7kg
Clean. Simple. Fast to calculate in your head.
Why Coaches Like Epley
Epley’s formula tends to be slightly generous; it pushes the estimate a little higher. For beginners and intermediate lifters doing moderate rep ranges (4–10 reps), this works well because it gives you a number that feels motivating without being completely unrealistic.
It also handles higher rep sets (10–15 reps) better than some other formulas. If you’re doing higher-volume work and want a rough ceiling estimate, Epley tends to hold up reasonably well.
One thing to know: Epley can slightly overestimate if you’re doing very low reps (1–3). When the rep count is already close to a max effort, the math gets a bit inflated.
The Brzycki Formula: A More Conservative Estimate
Matt Brzycki introduced his formula in 1993. He was a strength and conditioning coach at Princeton, and his formula was built around a slightly different mathematical approach.
1RM = Weight × (36 / (37 − Reps))
Same lifter, same set 100kg for 8 reps:
1RM = 100 × (36 / (37 − 8)) = 100 × (36 / 29) = 100 × 1.241 = 124.1kg
Not a huge difference from Epley, about 2–3kg in this case. But in strength training, 2–3kg matters when you’re programming percentages.
Why Coaches Like Brzycki
Brzycki’s formula is a bit more conservative and tends to be more accurate in the lower rep ranges (1–6 reps). If you’re doing a heavy triple or a tough set of five, Brzycki tends to land closer to your actual max.
There’s a catch, though. When rep counts get higher, around 10 and above, Brzycki starts to overestimate quite significantly. The denominator in the formula gets smaller fast, and the output inflates quickly.
Essentially, Brzycki is sharper at the heavy end, and Epley holds up better at higher rep ranges.
Epley vs Brzycki: A Direct Comparison
Here’s how both formulas behave across different rep ranges for the same 100kg lift:
Reps Epley 1RM Brzycki 1RM
3 110kg 109.1kg
5 116.7kg 115.9kg
8 126.7kg 124.1kg
10 133.3kg 130.9kg
12 140kg 140.6kg
15 150kg 180kg*
*At 15 reps, Brzycki’s formula jumps dramatically and becomes unreliable. This is a known limitation.
The takeaway here is clear: use Brzycki for lower rep work, use Epley for moderate-to-higher rep ranges.
How to Actually Apply This in Your Training
Knowing the formulas is fine. Knowing how to use them is better. Here’s a simple framework:
Step 1: Choose Your Testing Set Wisely
Don’t do 15 reps and try to calculate a max. It’s unreliable with both formulas. Aim for a rep range of 3–8 reps at a genuinely challenging weight, not your absolute limit, but hard enough that you couldn’t do many more.
A set of 5 solid reps at near-max effort gives you the cleanest data.
Step 2: Use the Right Formula for Your Rep Count
- 1–6 reps → use Brzycki
- 7–10 reps → either formula works, average them if you want
- 11+ reps → use Epley, or better yet, redo the test at a heavier weight
Step 3: Apply Percentages to Your Estimated 1RM
Most percentage-based programs (like 5/3/1, Texas Method, or Juggernaut) have you work at 65–90% of your 1RM. Once you have your estimated max, the math is simple:
- 80% of 125kg = 100kg working weight
- 70% of 125kg = 87.5kg working weight
This is how real strength training programs are built. You’re not guessing anymore, you’re training with intent.
Step 4: Retest Every 4–6 Weeks
Your 1RM estimate should be a living number. As you get stronger, it changes. Retest regularly, adjust your percentages, and keep pushing forward.
Practical Tips Most People Skip
Test on a good day. Your estimated 1RM will be off if you test after a terrible night’s sleep or at the end of a hard training week. Save your test sets for when you’re fresh.
Rest long enough between sets. When you’re working up to a heavy test set, rest at least 3–5 minutes between heavy attempts. Fatigue kills accuracy.
Use the same exercise consistently. Your squat 1RM and your leg press 1RM are completely different numbers. Always test the same lift for comparison.
Record everything. Weight, reps, estimated 1RM, date. Over months, this data tells you exactly how your muscle building is progressing. It’s your personal strength.
Don’t test on isolation exercises. These formulas are built for compound movements: squat, deadlift, bench, and overhead press. Using them for a bicep curl is inaccurate and kind of pointless.
Common Mistakes Lifters Make With 1RM Calculations
Mistake 1: Using too many reps. This is the big one. Someone does 15 reps on the bench, plugs it into a calculator, and gets a wildly inflated number. Then they try to train at 80% of that number and can’t hit their reps. Stick to 3–8 rep test sets.
Mistake 2: Not accounting for form breakdown. If your last 3 reps in an 8-rep set had terrible form, those reps shouldn’t count. The formula assumes each rep was properly executed. A set of 5 clean reps beats a set of 8 sloppy ones every time.
Mistake 3: Treating the estimate like an absolute truth. It’s an estimate. A very useful one, but still an estimate. Your real max on any given day depends on sleep, food, stress, warm-up quality, and about 20 other things. Use the number as a guide, not gospel.
Mistake 4: Never updating the number. Some lifters calculate their 1RM once in January and use it all year. By June, they’ve gotten significantly stronger, and their percentages are too easy. Retest, recalculate, keep progressing.
Mistake 5: Using the formula for high-fatigue sets. If you did 3 sets before your test set, your muscles are already tired. Test sets should come early in the session, after a thorough warm-up but before significant fatigue sets in.
Frequently Asked Question
Is the Epley or Brzycki formula more accurate overall?
Neither is universally more accurate. Brzycki is better for low-rep, heavy sets (1–6 reps). Epley holds up better across a broader rep range, especially above 8 reps. The best approach is to use Brzycki for your heavy days and Epley when working at higher rep ranges.
Can I use these formulas for any exercise?
Technically yes, but they’re most reliable for big compound lifts: squat, bench press, deadlift, overhead press, and barbell row. Isolation exercises like curls or lateral raises don’t lend themselves well to 1RM calculation.
What if my two formula results are very different?
If there’s a big gap between Epley and Brzycki results, it usually means you tested at a rep range where one formula starts to lose accuracy. The safest option: average the two results, or retest at 5 reps.
Do I ever need to test my actual 1RM?
Advanced powerlifters and competitive athletes sometimes do. For most gym-goers focused on muscle building and strength training, calculated estimates are safer and accurate enough. Real max testing carries injury risk; it’s rarely worth it outside of competition.
How often should I recalculate my 1RM?
Every 4–6 weeks is a solid habit. Some programs (like 5/3/1) have you recalculate each training cycle. Any time you notice your working weights feel significantly easier than they should, it’s time to retest.
Conclusion
At the end of the day, both the Epley and Brzycki formulas are useful tools and the difference between them in most real-world situations is smaller than people think.
Here’s the practical summary: use Brzycki when you’re working heavy and low (1–6 reps), and use Epley when your rep counts are moderate to higher. When in doubt, test at 5 reps and you’ll get reliable output from either formula.
What matters more than which formula you pick is that you actually use one consistently. Track your estimated 1RM, train at the right percentages, and retest regularly. That’s how gym progress compounds over time.