How to Calculate One Rep Max (Without Maxing Out)

To calculate your one rep max (1RM) without actually lifting a maximum weight, perform a set of 3–10 reps close to failure with good form, then plug the weight and reps into a formula. The two most common are Epley: 1RM = weight × (1 + reps ÷ 30) and Brzycki: 1RM = weight × 36 ÷ (37 − reps). For example, 60 kg for 8 reps gives an estimated 1RM of 76 kg (Epley) or about 74.5 kg (Brzycki). It is an estimate, not a guarantee, but it is far safer than a true max test.

If you do not want to do the maths yourself, our free one rep max calculator shows both formulas, their average and a full percentage table in kg or lb. Below we explain how the formulas work, how to get a reliable input set and how to use the result in your training.

What is a one rep max?

Your one rep max is the heaviest weight you can lift for a single repetition of an exercise with correct technique. It is a common way to describe strength and to plan training intensity. Many programs prescribe weights as a percentage of 1RM, such as "3 sets of 5 at 80 %".

You do not need to know your 1RM to make progress. Beginners can progress perfectly well with simple rep targets, as explained in our strength training for beginners guide. But an estimated max is a handy benchmark for tracking strength and for following percentage-based plans later on.

Why estimate instead of testing?

A real 1RM test has drawbacks, especially for beginners:

• Technique tends to break down on true maximum attempts.
• It needs a safe setup: a spotter, safety bars in a rack or an experienced coach.
• It is fatiguing and can interfere with your normal training for days.
• Beginner strength changes quickly, so a tested max is out of date within weeks.

An estimate from a submaximal set avoids all of that. You get a useful number while lifting a weight you can control. If you ever do want to test a true max, do it with experienced supervision and proper safety equipment, and skip it entirely if you have any injury or health concern; check with a doctor first if you are unsure.

The two main formulas

Epley formula

1RM = weight × (1 + reps ÷ 30)

Example: 80 kg × 5 reps 80 × (1 + 5 ÷ 30) = 80 × 1.167 ≈ 93.3 kg

Brzycki formula

1RM = weight × 36 ÷ (37 − reps)

Example: 80 kg × 5 reps 80 × 36 ÷ 32 = 90 kg

Both formulas assume your set was taken close to failure. If you stopped with four or five reps left in the tank, the result will underestimate your true max.

How the formulas compare

Here is the same 100 kg set at different rep counts, rounded to one decimal place:

Reps at 100 kg	Epley	Brzycki	Average
1	103.3	100.0	101.7
3	110.0	105.9	107.9
5	116.7	112.5	114.6
8	126.7	124.1	125.4
10	133.3	133.3	133.3
12	140.0	144.0	142.0

Notice that the formulas agree closely around 10 reps and diverge more at the extremes. Epley also gives slightly more than the lifted weight even for a single rep, which is a quirk of the formula. For a true single, simply use the weight you lifted. This is why the one rep max calculator shows both values and their average rather than pretending one number is exact.

How to get a good input set

The estimate is only as good as the set you feed it. Follow these steps:

1. Warm up properly. 5 minutes of easy cardio, then 2–3 lighter sets of the exercise.
2. Choose a weight you can lift for about 3–10 reps. Around 5–8 reps is a sweet spot for many people.
3. Lift with strict, consistent form. No bouncing, no half reps.
4. Stop when your form would break down, or when you have at most one clean rep left.
5. Write down the weight and the number of good reps.

Avoid estimating from sets above 12 reps. Muscular endurance plays a bigger role there and the formulas become much less reliable.

Using your 1RM: a percentage chart

Once you have an estimated max, you can use percentages to choose training weights. The rep ranges below are rough rules of thumb; individual results vary, and they also vary from exercise to exercise.

% of 1RM	Roughly how many reps	Typical use
100 %	1	Max effort (experienced lifters only)
95 %	2	Very heavy singles and doubles
90 %	3–4	Heavy strength work
85 %	5–6	Strength
80 %	7–8	Strength and muscle
75 %	9–10	Muscle building
70 %	11–12	Muscle building
65 %	13–15	Higher reps, technique
60 %	15+	Warm-ups, technique practice
50 %	20+	Warm-ups

Worked example: your estimated squat 1RM is 100 kg and your plan says "3 sets of 6 at 80 %". That is 80 kg. Because the chart says 80 % is roughly a 7–8 rep weight, 6 reps should leave you about 1–2 reps in reserve, which is a sensible training effort.

Converting between kg and lb

The formulas work in any unit. Just keep the unit consistent. To convert, 1 kg ≈ 2.205 lb.

kg	lb (approx.)
20	44
40	88
60	132
80	176
100	220

The calculator has a kg/lb switch, so you do not need to convert manually.

How to track your estimated 1RM over time

A great use of the estimate is comparing sets that are otherwise hard to compare. Say your log shows:

Week	Set	Estimated 1RM (average)
1	60 kg × 8	≈ 75 kg
4	62.5 kg × 8	≈ 78 kg
8	70 kg × 5	≈ 80 kg

Even though the reps changed, you can see a steady upward trend. That is progressive overload in action. Recalculate every 4–8 weeks or whenever you beat a rep record.

Limitations to keep in mind

• Individual differences: some people can do many reps at a given percentage, others very few. The formulas average this out.
• Exercise differences: estimates tend to be more useful on big compound lifts (squat, bench press, deadlift) than on small isolation exercises or machines.
• Fatigue and technique: a set done at the end of a long workout or with sloppy reps gives a misleading result.
• Not a target to chase: your estimated max is a planning tool. Do not try to lift it just because a formula produced the number.

Common mistakes

• Using a set of 15–20 reps and treating the result as precise.
• Counting reps with broken form or partial range of motion.
• Re-testing too often and chasing numbers instead of training.
• Planning heavy percentages from an estimate that is months old.
• Attempting a true max without a spotter or safety bars.

Quick checklist

• I warmed up with 2–3 lighter sets
• My test set was 3–10 reps, close to failure, with good form
• I entered the weight and reps in the one rep max calculator
• I use the average of Epley and Brzycki as a rough guide
• I base training weights on percentages with a margin for error
• I recalculate every 4–8 weeks

Calculating your one rep max from a submaximal set gives you most of the benefits of a max test with very little of the risk. Use it as a guide, keep training with good form, and let your log show you the progress. For a plan to apply those numbers, try our 3 day full body workout for beginners.