One Rep Max Calculator — Free 1RM Calculator with AI Insights
This one rep max calculator uses three published strength formulas — Epley, Brzycki, and Lander — to estimate your 1RM from any weight and rep combination, plus a full training percentage breakdown.
Your lift details
Enter the weight and reps from a recent set taken close to failure.
What is One Rep Max?
One rep max (1RM) is the maximum weight you can lift for exactly one full repetition of an exercise with correct form. Because testing a true 1RM is fatiguing and carries injury risk, lifters commonly estimate it from a lighter set taken close to failure using a validated formula — that's exactly what this calculator does.
Each formula below was developed from data on lifters performing multiple-rep sets and extrapolating the load that would correspond to a single rep. They differ slightly in how they weight the relationship between reps and load, which is why this calculator shows all three side by side rather than presenting a single number as definitive.
| Formula | Equation | Most accurate when |
|---|---|---|
| Epley | 1RM = w × (1 + reps/30) | Widely used across rep ranges; tends to estimate slightly higher at higher reps. |
| Brzycki | 1RM = w × 36 / (37 − reps) | Often more conservative for sets in the 5-10 rep range. |
| Lander | 1RM = (100 × w) / (101.3 − 2.67123 × reps) | Tends to fall between Epley and Brzycki for moderate rep counts. |
| Average | (Epley + Brzycki + Lander) / 3 | A balanced default that smooths individual formula bias. |
How the One Rep Max Calculator Works — The Formula
This calculator runs your weight and rep count through three independent formulas, then reports each one plus their average. Here's exactly what's behind each estimate:
Epley: 1RM = w × (1 + reps / 30)
Brzycki: 1RM = w × 36 / (37 − reps)
Lander: 1RM = (100 × w) / (101.3 − 2.67123 × reps)
- w
- The weight you lifted, in your chosen unit (kg or lb).
- reps
- The number of complete repetitions performed in that set (1-12).
- 1RM
- The estimated maximum weight you could lift for a single repetition.
Worked example: say you bench pressed 100kg for 5 reps.
- Epley: 100 × (1 + 5/30) = 100 × 1.1667 = 116.7kg
- Brzycki: 100 × 36 / (37 − 5) = 3600 / 32 = 112.5kg
- Lander: (100 × 100) / (101.3 − 2.67123 × 5) = 10000 / 87.94 = 113.7kg
Averaging those three gives ≈ 114.3kg — this calculator's default "Average" formula would report this as your estimated 1RM.
Plugging in a set of 15-20 reps. All three formulas were derived from lower-rep data, and the relationship between reps and load flattens out at high reps — the Brzycki formula even becomes mathematically undefined at 37 reps (division by zero). For reliable estimates, use a set of 1-12 reps taken close to muscular failure.
How to Use the One Rep Max Calculator
- Enter the Weight lifted for your set, and choose kg or lb from the unit dropdown.
- Enter the Reps performed in that set — a whole number from 1 to 12.
- Choose your Lift type (Bench Press, Squat, Deadlift, or Overhead Press) so your results are labeled correctly.
- Pick a Formula — Average is recommended for most lifters, or choose a single formula if your program specifies one.
- Click Calculate to see your results instantly.
- Scroll to the AI Insights section to understand what your result means.
How to Interpret Your One Rep Max Results
What a Good Result Looks Like
As a general guideline, intermediate lifters often work toward a bench press 1RM around their bodyweight, a squat 1RM around 1.25-1.5× bodyweight, and a deadlift 1RM around 1.5-2× bodyweight. Novice lifters typically sit below these multiples, while advanced and competitive lifters often exceed them. These ranges vary widely by sex, training age, body composition, and experience — treat them as a rough orientation, not a target you must hit.
| Lift | Novice | Intermediate | Advanced |
|---|---|---|---|
| Bench Press | ~0.5-0.75× bodyweight | ~1× bodyweight | ~1.5×+ bodyweight |
| Squat | ~0.75-1× bodyweight | ~1.25-1.5× bodyweight | ~2×+ bodyweight |
| Deadlift | ~1× bodyweight | ~1.5-2× bodyweight | ~2.5×+ bodyweight |
| Overhead Press | ~0.35-0.5× bodyweight | ~0.65-0.8× bodyweight | ~1×+ bodyweight |
Warning Signs in Your Results
If your reps were close to 12, treat the estimate as a rough ceiling rather than a precise number — formula accuracy declines as reps increase. If you notice a large spread between the Epley, Brzycki, and Lander estimates (more than roughly 5-8% apart), it usually means the rep count you entered is near the edge of where these formulas agree — retesting with a set of 3-5 reps will generally tighten the spread and give a more trustworthy estimate.
How to Improve Your Result
- Train in the 70-85% range. Working at 70-85% of your estimated 1RM for 4-8 reps builds the strength that directly raises your 1RM over time.
- Improve technique under load. A more efficient bar path or bracing technique can immediately increase the weight you can move for the same effort.
- Progressively overload. Add small amounts of weight or reps week to week — even 1-2.5kg per session compounds significantly over months.
- Retest periodically. Recalculate your 1RM every 4-8 weeks using a fresh 3-5 rep set to track real progress and adjust your training percentages.
One Rep Max Calculator Examples
One Rep Max Formula: Epley Method Example
A lifter completes a deadlift set and wants to check their 1RM specifically using the Epley method, which their program uses for percentage targets.
- Weight lifted: 140kg
- Reps performed: 4
- Lift type: Deadlift
- Formula: Epley
Result: 1RM ≈ 158.7kg (140 × (1 + 4/30)).
What this means: the lifter's program-specific percentages should be calculated from this Epley figure, not the average, since that's what their plan was built around.
What to do next: use the training percentage table to find the working weights for upcoming deadlift sessions.
Bench Press Max Calculator Example
A lifter benches 80kg for 8 reps and wants a realistic estimate of their bench press max using the default average formula.
- Weight lifted: 80kg
- Reps performed: 8
- Lift type: Bench Press
- Formula: Average of all three
Result: 1RM ≈ 102.7kg (averaging Epley ≈ 101.3kg, Brzycki ≈ 99.3kg, Lander ≈ 107.6kg).
What this means: at 8 reps the three formulas already show some spread — the average gives a balanced middle estimate.
What to do next: if precision matters, retest with a 3-5 rep set to narrow the range between formulas.
Percentage of 1RM Training Calculator Example
A lifter has an estimated 1RM of 120kg on the squat and wants to plan a hypertrophy block at 70-80% of that max.
- Estimated 1RM: 120kg
- Target range: 70-80% of 1RM
- Goal: hypertrophy (8-12 reps)
Result: working weight 84kg-96kg for 8-12 reps per set.
What this means: any squat session loaded between 84kg and 96kg, taken to 8-12 reps near failure, falls within the hypertrophy training zone for this lifter.
What to do next: use the full training percentage table to plan strength (80-85%) and near-max (90-95%) phases as the program progresses.
This calculator provides an estimate only and is not medical, fitness, or coaching advice. Formula-based 1RM estimates can differ from your true one rep max, especially outside the 1-12 rep range. Do not attempt a true 1RM lift without a qualified spotter, proper warm-up sets, and sound technique. If you are a beginner, returning from injury, or have any health condition that could be affected by maximal-effort lifting, consult a qualified coach, trainer, or healthcare professional before testing or training near your max.
Frequently Asked Questions about the One Rep Max Calculator
What is one rep max and why does it matter?
Your one rep max (1RM) is the heaviest weight you can lift for a single complete repetition of an exercise with good form. It matters because most strength programs prescribe training loads as a percentage of your 1RM — for example, "work up to 5 reps at 80% of 1RM" — so knowing this number lets you calculate exact training weights for hypertrophy, strength, or power phases without guesswork.
Which 1RM formula is most accurate?
No single formula is universally "most accurate" — each was derived from different lifter populations and rep ranges. The Brzycki formula tends to be slightly more conservative at higher reps, while Epley is widely used and tends to run a bit higher. Lander often sits between the two. Averaging all three (the default in this calculator) smooths out individual formula bias and is a reasonable middle-ground estimate for reps between 1 and 10.
How do I use my 1RM to program workouts?
Multiply your estimated 1RM by the percentage your program calls for. For example, if your 1RM is 100kg and your program prescribes "3 sets of 8 at 75%," your working weight is 75kg. This calculator's training percentage table does that math for you across the 50-95% range, with typical rep ranges for endurance, hypertrophy, strength, and near-max work.
How accurate are 1RM formulas, and what are their limitations?
Formula-based 1RM estimates are typically within about 5-10% of a true tested max for reps in the 1-10 range, but accuracy drops sharply above 10-12 reps because the relationship between reps and load becomes less linear. Estimates also assume the set was taken close to failure with good form — a set with reps left "in the tank" will underestimate your true max.
What formulas does this 1RM calculator use?
This calculator uses three peer-referenced formulas: Epley (1RM = w × (1 + reps/30)), Brzycki (1RM = w × 36 / (37 − reps)), and Lander (1RM = (100 × w) / (101.3 − 2.67123 × reps)). All three are computed from the same weight and rep inputs, shown side by side, and averaged so you can see the spread between estimates rather than relying on a single number.
How does this compare to other 1RM calculators or the Wendler/Lift method?
Most online 1RM calculators use one of these same three formulas (often just Epley), so results should be close to other tools when reps match. Some programs, like Wendler 5/3/1, deliberately use a "training max" set at 90% of your calculated 1RM to build in a safety margin — this calculator gives you the raw estimate, and you can apply that kind of buffer yourself if your program calls for it.
What if I do very high reps or I'm an untrained lifter?
For sets above 12 reps, this calculator will show a validation message because formula accuracy degrades significantly — at 15-20 reps, estimates can be off by 15% or more. For untrained or new lifters, technique and bar speed are less consistent set-to-set, so even a "valid" 5-rep estimate may swing widely between sessions. In both cases, treat the output as a rough starting point, not a precise number.
Is it safe to test my actual one rep max?
Testing a true 1RM carries real injury risk, especially without a spotter, a proper warm-up, and good technique under maximal load. Most lifters — and virtually all beginners — get equally useful numbers from a formula-based estimate using a comfortable 3-5 rep set. If you do attempt a true max test, do it with a qualified spotter or coach present and only after several progressively heavier warm-up sets.