Enter the weight you lifted and how many reps you completed. This calculator estimates your one-rep max using five established formulas and gives you a percentage chart you can use to program your training. Click any row to load that weight into the plate calculator and see exactly what to put on the bar.
Click a row to load plates
| % | Weight | Reps |
|---|
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is the foundational number for most percentage-based strength programs. Wendler 5/3/1 prescribes every working set as a fraction of your 1RM. Texas Method, nSuns, and similar intermediate programs do the same. Without a reliable 1RM, you are guessing at your training weights, which leads to sessions that are either too easy to drive progress or too taxing to recover from.
Testing a true 1RM — warming up methodically, then attempting a single limit rep — requires maximal effort and carries injury risk, particularly for less experienced lifters who have not developed consistent technique under heavy load. A miss near max weight can be dangerous on squats and bench press without a spotter or safety bars in place.
Estimating your 1RM from a submaximal set is standard practice for good reason. It is safer, requires no special setup or spotter, fits naturally into a regular training session, and is nearly as useful for programming purposes. Take a set you completed with genuine effort — ideally in the 3–8 rep range — enter the weight and reps here, and you will get a reliable estimate within a few percent of your true max. The estimates become less accurate above 10 reps because muscular endurance and fatigue play an increasingly large role, but for sets of 2–8 reps the common formulas are typically within 5% of a true tested maximum.
Each formula approaches the weight-reps relationship differently. Epley (1985) and Brzycki (1993) are the most widely cited in the strength training literature and tend to agree closely for sets in the 3–6 rep range. Both model the 1RM as a function that increases roughly linearly with reps performed, but they diverge as rep counts climb above 8–10.
Lander's formula is slightly more conservative — it produces a lower 1RM estimate from the same input, which some lifters find more accurate when training at higher rep ranges. Lombardi applies a fractional exponent (reps^0.10) to the rep count, which compresses the curve and makes the formula more forgiving on higher rep sets. O'Conner is the simplest of the five, using a flat scaling factor that consistently produces slightly lower estimates than Epley.
Using the average of all five formulas smooths out the individual biases and tends to produce estimates that are more consistent across a wider range of rep counts. No formula is universally correct — every lifter's fatigue curve is slightly different. If you know from experience that one formula consistently tracks your actual performance better than the others, you can weight it accordingly. The plate calculator and percentage chart in this tool use the averaged estimate by default.
Brzycki and Epley are the most validated in research. For sets under 10 reps, both tend to come within 5% of a true 1RM. They diverge more at higher rep counts, which is why the average across formulas is more reliable than any single one.
Only if you're experienced, well-warmed-up, and have a spotter or safety equipment. For programming purposes, an estimate from a 3–5 rep set is safer and nearly as useful. Pushing to a true max taxes your central nervous system and takes longer to recover from than a hard working set.
Every 4–6 weeks, or whenever you hit a notable PR on a working set. If you're on a linear progression program, your weights are going up frequently enough that you may want to update monthly.
Mental math between sets is error-prone and wastes time. Seeing the exact plate breakdown eliminates mistakes, especially for odd weights like 237.5 lb. The visual diagram also makes it faster to load the bar correctly.
Yes, toggle to kg at the top. All calculations and plate sizes adjust automatically. The plate options switch to standard kg denominations (25, 20, 15, 10, 5, 2.5, 1.25 kg) with a 20 kg barbell.