How to calculate your 1RM (one-rep max) and use it to pick your weights

Your 1RM (one-rep max) is the heaviest weight you can lift once in an exercise, with good form. It is the reference almost every strength program uses to tell you how much to load: when a routine says "4 sets of 6 at 80%", that 80% is of your 1RM.

The good news is that you do not need to test your true max to know it. You can estimate it from a set of several reps, with less risk and nearly the same practical value.

Why estimate it instead of testing it

Testing a true 1RM makes sense for competitive lifters or people with years of experience, and even then it is done with a spotter. For everyone else, estimating is the better choice:

• It is safer. A set of 3 to 6 reps puts far less strain on your technique than a max attempt.
• It is less fatiguing. A max test can leave you drained for days; a heavy set fits inside a normal workout.
• It is accurate enough. You do not need the exact number to pick your weights: being within a couple of kilos is plenty.

The two most common formulas

You need two numbers from the same set: the weight you used and the reps you completed.

Epley formula

1RM = weight × (1 + reps ÷ 30)

Brzycki formula

1RM = weight × 36 ÷ (37 − reps)

An example: you squat 80 kg and get 6 reps before you cannot do another one with good form.

• Epley: 80 × (1 + 6 ÷ 30) = 80 × 1.2 = 96 kg
• Brzycki: 80 × 36 ÷ 31 = 92.9 kg

Both give similar numbers and neither is "the right one": they are approximations. Pick one and stick with it, so your estimates stay comparable over time.

How to do the test set

The estimate is only as good as the set you feed it. To make it useful:

1. Warm up properly. A few minutes of general activity, then 2 or 3 ramp-up sets with increasing weight and low reps.
2. Pick a weight you can move 3 to 6 times. The formulas are most accurate at low reps; above 10 the error grows considerably.
3. Take the set close to failure, but not to an ugly failure. Stop when you feel the next rep would break your form. That is the last rep you count.
4. Write down the weight and reps. Without a log, next time you will be guessing.

Do it on the compound lifts where 1RM is used the most: squat, bench press, deadlift, overhead press or row. For isolation exercises (biceps curls, lateral raises), 1RM is rarely used for programming.

1RM percentage chart

Once you have your 1RM, this chart tells you roughly how many reps you can do at each percentage, and the other way around:

These are reference values taken to failure. Everyone deviates a little: some people get 12 reps at 75%, others get 8. If a weight feels clearly easier or harder than the chart says, trust what happens on the bar.

How to use it to pick your weights

With your estimated 1RM, choosing the weight for each set is a multiplication. Continuing the squat example (1RM ≈ 95 kg):

• Strength (3 to 5 reps): 80% to 90%, so 76 to 85 kg.
• Hypertrophy (6 to 12 reps): 67% to 85%, so 64 to 81 kg.
• Technique or warm-up: 50% to 60%, so 48 to 57 kg.

Always round to the nearest plate your gym has, and when in doubt, round down. Since you should not take every set to failure, the usual approach is to work slightly below what the chart says and leave one or two reps in reserve.

How often to update it

Your 1RM changes as you train. Recalculate it every 4 to 8 weeks, or at the end of a training block. You do not need a special day: use the heaviest set from a normal session and run it through the same formula as always.

If the number goes up, you are making progress. If it stalls for several weeks in a row, it is time to review how you are applying progressive overload.

Track your 1RM in Athlo.fit

In Athlo.fit you can save your 1RM for each exercise and use it to calculate the weights in your routines, so every set has a concrete weight instead of a percentage to work out on the spot. And since every session is logged, you can see how your numbers evolve week by week.

Just getting started? Check out this 3-day full body workout for beginners.