Estimate the maximum weight you could lift for a single rep based on a set you've already done, then use the percentage table to plan your training weights.
As a rough guide, strength training often uses 85%+ of 1RM for 1–5 reps, while hypertrophy training uses 65–80% for 6–12 reps. Since this is an estimate, always use a spotter when actually testing a true max.
The 1RM is the reference point programmes are written against. "80% of your squat" needs a squat number before it means anything.
Actually testing one is costly. It requires full recovery, a long warm-up ladder, and a maximal attempt that carries injury risk and heavy central fatigue. For beginners whose technique is still forming, the risk is higher again.
So the number is inferred from lighter work instead. Knowing what you can lift for five reps places your one-rep maximum inside a fairly narrow band.
Epley: 1RM = weight × (1 + reps ÷ 30). It scales linearly with reps. 100 kg for 5 gives 100 × (1 + 5/30) = 116.7 kg.
Brzycki: 1RM = weight ÷ (1.0278 − 0.0278 × reps). The same set gives 100 ÷ (1.0278 − 0.139) = 112.6 kg.
Below about five reps the two agree within a few kilograms. They diverge as reps climb, converge again near ten, and separate sharply beyond that as Brzycki's denominator shrinks.
Brzycki's denominator reaches zero at 37 reps, where the formula becomes mathematically meaningless. Either way, use these estimates from sets of ten or fewer.
Muscle fibre composition varies. A fast-twitch-dominant lifter has a high maximum and poor rep endurance, so extrapolating from a five-rep set underestimates their true 1RM. Slow-twitch-dominant lifters show the opposite bias.
Lifts differ too. Deadlifts recruit large muscle groups and tax the nervous system heavily, so reps fall away quickly and the estimate tends to read low. Machine work like leg press produces more reps and reads high.
Training age matters. Experienced lifters have adapted to maximal intensity and sit relatively higher at 1RM; novices sit relatively lower.
Treat the output as a ±5–10% band. Use it as a starting point and correct it against a few weeks of actual training performance.
Maximal strength: 85–100% of 1RM, 1–5 reps, 3–5 minutes between sets. The adaptation being trained is largely neural.
Hypertrophy: 65–85%, 6–12 reps, 60–90 seconds of rest.
Muscular endurance: 50–65%, 15 or more reps, 30–60 seconds of rest.
These bands are conventions, not laws. Sets taken near failure produce hypertrophy at lower percentages too, and a growing body of work points to total volume mattering more than the specific load. Percentages are a convenient scale for intensity, nothing more.
Do not do it alone. A failed bench press pins the bar on your chest. Without a spotter, use a rack with safety bars.
Warm up properly: 8–10 light reps, then 5 at 50%, 3 at 70%, 1 at 85%, then attempts — resting 3–5 minutes between them.
An attempt with broken form does not count. Weight moved with a bounce or a rounded back is not a one-rep max; it is an injury waiting to happen.
Under six months of training, skip maximal testing entirely. Technique is not stable yet, and estimates are more than adequate for programming.
It predicts your 1RM from the weight lifted and the reps performed in a set. This calculator uses the Epley formula, and the guide below compares it with Brzycki.
Estimates are most accurate at lower rep ranges (around 1–10 reps). Above that, fatigue makes the prediction less reliable, so treat it as a guide.
It predicts 1RM from the weight lifted and the reps performed in a single set, using the Epley formula. The guide below compares it with Brzycki.
What this tool bases its numbers on, and how far those numbers go.
This calculator uses Epley: 1RM = weight × (1 + reps ÷ 30). The percentage table multiplies that estimated 1RM by each ratio. Brzycki is explained below for comparison only and is not what the screen shows.100 kg for 5 reps gives 100 × (1 + 5/30) = 116.7 kg. The same set comes to 112.6 kg by Brzycki, a figure this calculator does not display.