How to Estimate Your 1RM Without Maxing Out

You can estimate your one-rep max without ever loading it on the bar: take a hard set of 3 to 6 reps, write down the weight and the reps, and put them through a standard formula. Epley (weight × (1 + reps / 30)) and Brzycki (weight × 36 / (37 − reps)) both land within a few percent of a tested max for sets in that range. The 1RM calculator runs both, plus Lombardi, from one set.

Why estimate instead of test

A true one-rep max test is a skill and a stressor. It needs a long warm-up, a spotter or safety arms, a day when you are fresh, and a program that has room for the fatigue afterwards. Most lifters only need the number for two things: setting percentages for a block, and seeing whether they are stronger than last month. An estimate does both jobs well enough, and you get a fresh one from every heavy session for free.

There is also a practical point. A tested max is one data point from one day. An estimated max from your weekly top set is a trend line. Over a block of training, the trend tells you more than any single attempt.

Step 1: pick a set that qualifies

The estimate is only as good as the set behind it. Three conditions matter:

3 to 6 reps. Prediction equations were built from sets like these, and in LeSuer and colleagues’ comparison of seven equations against tested maxes in the bench press, squat and deadlift, the equations tracked closely for low-rep sets. Reynolds and colleagues found the 5RM predicted the 1RM better than the 10RM or 20RM, and advised against feeding more than 10 reps into a linear equation.
Close to failure. The formulas assume the set ended because you could not do another good rep. A set of 5 with three left in the tank will read as a lower max than you have.
Full, consistent technique. A high squat or a bounced bench counts reps you could not do properly. Use the same standards you would want in a max attempt.

A good candidate is the last work set of a heavy day, for example 100 kg × 5 on the squat with one rep left.

Step 2: run the formula

With 100 kg for 5 reps:

Epley: 100 × (1 + 5/30) = 100 × 1.167 = 116.7 kg
Brzycki: 100 × 36 / (37 − 5) = 3,600 / 32 = 112.5 kg

A 4 kg spread between the two is normal, and it is the size of uncertainty you should expect from any estimate. For setting loads, the lower number is the safer starting point. For tracking progress, it does not matter which you pick, as long as you never switch. The guide to 1RM formulas explains where each equation came from and why they drift apart above 10 reps.

If you prefer a table to a formula, the same pair of numbers gives a quick mental shortcut: a 5-rep max is roughly 85 to 89 percent of a 1RM, a 3-rep max roughly 90 to 94 percent. Dividing your set weight by that percentage gives the estimate.

Step 3: correct for reps in reserve

Not every heavy set is taken to the limit, and that is fine. If you log RPE, you can still use the set. The resistance-training RPE scale described by Zourdos and colleagues counts reps in reserve: RPE 10 means no reps left, RPE 9 one left, RPE 8 two left. Helms and colleagues laid out how to use it for load selection.

The correction is simple. Add the reps in reserve to the reps you did, then run the formula on the total:

100 kg × 5 at RPE 8 → 5 reps + 2 in reserve = a 7-rep effort.
Epley: 100 × (1 + 7/30) = 123.3 kg.

The RPE chart does this step for you: enter the weight, the reps and the RPE, and it returns the estimated max and a load for your next set. Two cautions apply. Lifters rate RPE more accurately the closer they are to failure, so a set at RPE 6 gives a shakier estimate than one at RPE 9. And a half-point of RPE on a long set moves the estimate more than on a short one, which is another reason to keep estimating sets to about six reps.

Step 4: use the number carefully

For setting loads. Round the estimate down to the nearest plate increment before taking percentages from it. If a block prescribes 5 × 5 at 80 percent, and your estimate is 116.7 kg, work from 115 and load 92.5 kg. A block that starts slightly light costs you nothing; one that starts slightly heavy costs you the block. Programs built on a “training max” of about 90 percent of the estimate exist for exactly this reason, and the lifting log generator uses that approach for its wave program.

For tracking progress. Write the e1RM next to your top set every week. Use the same formula, the same lift and a similar rep range. If 100 × 5 in week 1 becomes 102.5 × 5 in week 4 at the same RPE, Epley moves from 116.7 to 119.6 kg: a real, visible gain without a single max attempt. The guide to tracking progressive overload shows where the number fits in a log.

For comparing lifts. Estimates are less reliable for some movements than others. In LeSuer’s data every equation underestimated the deadlift, and in general lifts with a longer range of motion or more technique involved behave differently from the average the formulas describe. Treat an estimated deadlift max as more conservative than an estimated bench max.

When a real test still makes sense

Estimates are enough for most training. Test a true max when a competition requires it, when a program’s percentages are built around a tested number, or when you want to practise the skill of a maximal attempt. Do it at the end of a block, after a lighter week, with a structured warm-up (see warm-up sets) and with spotters or safety arms set. If anything hurts, stop and get it checked by a qualified professional.

A one-minute routine

After your last heavy work set, note weight, reps and RPE.
If RPE was below 10, add the reps in reserve to the reps done.
Enter the set in the 1RM calculator (or the RPE chart) and read off the Epley and Brzycki estimates.
Write the lower one in your log next to the set.
Next week, compare.

Questions lifters ask

How many reps should I do to estimate my 1RM?

Three to six reps, taken to within a rep or two of failure, give the most reliable estimate. Below three reps you are nearly maxing anyway; above about ten the formulas disagree with each other and with tested maxes.

Is an estimated 1RM accurate enough to set training percentages?

For most programs, yes. A 3 to 5 percent error on a 100 kg estimate is 3 to 5 kg, and percentage-based programs round loads to the nearest plate anyway. If week one feels too heavy, lower the estimate by 5 percent and carry on.

Should I use Epley or Brzycki?

Either, as long as you keep using the same one. For sets of 2 to 9 reps Brzycki gives a slightly lower number than Epley, so it is the more cautious choice for setting loads. They give the same answer at 10 reps.

Can I estimate my 1RM from a set that was not close to failure?

Yes, if you logged the RPE. A set of 5 at RPE 8 means two reps were left, so it counts as a 7-rep effort. Plug 7 reps into the formula, or use the RPE chart, which does this step for you.

Sources

Brzycki M. Strength Testing - Predicting a One-Rep Max from Reps-to-Fatigue . Journal of Physical Education, Recreation & Dance, 1993;64(1):88-90
LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift . Journal of Strength and Conditioning Research, 1997;11(4):211-213
Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry . Journal of Strength and Conditioning Research, 2006;20(3):584-592
Zourdos MC, Klemp A, Dolan C, Quiles JM, Schau KA, Jo E, Helms E, Esgro B, Duncan S, Garcia Merino S, Blanco R. Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve . Journal of Strength and Conditioning Research, 2016;30(1):267-275
Helms ER, Cronin J, Storey A, Zourdos MC. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training . Strength and Conditioning Journal, 2016;38(4):42-49

This guide is general education about training, not medical advice. If something hurts, stop and get it checked by a qualified professional.