Key Takeaways
- Your leg press 1RM is the heaviest load you can press once through a full range. This page estimates it from a hard set of 2 to 10 reps to failure, so you don't have to test a true max.
- Two equations were built on the leg press itself: Reynolds (2006) for 5 or 10 reps[1] and Kemmler (2006) for 3 or more reps[2]. The page shows them next to seven general equations that were built on other lifts[3].
- The equations disagree. For 100 kg for 5 reps, Reynolds gives 124 kg and Kemmler gives 108 kg. I can't tell you which is closer for you, so the page shows the spread.
- Reynolds built his equations on one plate-loaded Cybex machine and discourages using them on other leg presses[1]. A number from one machine doesn't carry over to another.
- I found no leg press strength standards I could verify, so the page doesn't rate you as beginner or advanced. Optional body weight gives a plain ratio instead.
What a Leg Press Max Is
A one-rep max (1RM) is the most weight you can lift for one clean rep. On the leg press, that means the most load you can push from the bottom position to full extension.
Testing it directly is hard on the body. The American Council on Exercise says lifting maximum loads isn't recommended for most people, because the risk outweighs the benefit[5]. So most people estimate it from a set of several reps instead.
The estimate is only as good as the set behind it. The set has to go to failure, the reps have to be clean, and you should use the same machine each time.
How the Calculator Works
What happens when you press Calculate
- You enter the load and the reps you completed to failure, from 2 to 10.
- Kemmler's equation runs for 3 or more reps[2]. Reynolds' equation runs only if you did exactly 5 or 10 reps[1].
- Seven general equations also run[3].
- By default the page averages every equation that applies. The calculation method list lets you use the leg press equations only, or any one equation on its own.
- The page shows each equation's result, which ones fed the headline number, and the lowest and highest.
Worked example: 150 kg for 5 reps
Reynolds: 1.09703 × 150 + 14.2546 = 178.8 kg
Kemmler: 150 × 1.0802 = 162 kg
Epley: 150 × (1 + 0.0333 × 5) = 175 kg
Brzycki: 100 × 150 ÷ (102.78 − 2.78 × 5) = 168.8 kg
Reynolds works in kilograms, so the page converts pounds to kilograms before applying it, then converts back. The average is a plain summary. It is not a validated estimator.
| Equation | Form | Built on | Reps accepted here |
|---|---|---|---|
| Reynolds 2006 | 1RM = 1.09703 × 5RM + 14.2546 (kg); 10RM: 1.2091 × 10RM + 38.0908 | 70 adults aged 18 to 69, one plate-loaded leg press | 5 or 10 reps |
| Kemmler 2006 | w × (0.988 + 0.0104r + 0.00190r² − 0.0000584r³) | 70 trained women, age 57.4 ± 3.1 | 3 to 10 reps |
| Epley | 1RM = w × (1 + 0.0333 × r) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| Brzycki | 1RM = 100 × w ÷ (102.78 − 2.78 × r) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| Lander | 1RM = 100 × w ÷ (101.3 − 2.67123 × r) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| Lombardi | 1RM = w × r^0.1 | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| Mayhew | 1RM = 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| O'Conner | 1RM = w × (1 + 0.025 × r) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
| Wathan | 1RM = 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) | Untrained students on the bench press, squat and deadlift | 2 to 10 reps |
Equations used and who they were built on.
Forms of the seven general equations are as printed in LeSuer et al. (1997)[3]. Reynolds also published a 20-rep equation, which the page doesn't use because it stops at 10 reps.
How Accurate It Is on the Leg Press
Reynolds and colleagues tested 70 adults on a plate-loaded leg press. A 5RM predicted the 1RM best, with a standard error of 16.16 kg. A 10RM gave 26.13 kg and a 20RM 29.41, so the error grew with the reps[1].
Adding body size, sex or training volume did not significantly improve the prediction[1]. In 20 other people, Brzycki, Lander and O'Connor all read low on the leg press[1].
Epley, Reynolds' own equations and one by Abadie had the smallest misses, with a slight tendency to read high. Lombardi and Mayhew were less accurate than the linear equations[1].
Kemmler's group reported an average miss of 1.5 to 3.1% across four machines in trained women aged about 57, and no change in accuracy between 3 and 20 reps[2]. I could only read the abstract, so I haven't seen the leg press numbers on their own.
Where the two leg press equations part ways
At 100 kg for 5 reps, Reynolds gives 124 kg and Kemmler gives 108 kg. The groups differ: mixed adults on one machine against trained women in their late 50s.
Reynolds' equation also has a fixed 14.2546 kg intercept. I can't say which is closer for you, so use the range.
Older adults need a separate note. Knutzen and colleagues tested 51 adults aged 70.7 ± 6.1 years on 11 machine lifts, using sets of 7 to 10 reps[4]. The abstract doesn't break out the leg press on its own.
Every equation read low, and for lower-body lifts the correlation with the real 1RM was only 0.60 to 0.80[4]. If you are in that age group, expect the estimate to come in under your true max.
Why Your Machine Matters
Reynolds used a nonadjustable Cybex plate-loaded squat press, with a 1-second lift and 1-second lower. The authors say they discourage using their equations on other leg press equipment, or with a different tempo[1]. I found no study that converts a leg press max from one machine to another.
- Compare like with like. Estimate on the machine you train on, and retest on it.
- Count the load one way. Plates only or plates plus sled both work, as long as you always log it the same way. I have no figure for any machine's sled weight, so the page doesn't guess one.
- Count full reps only. Reynolds did not count partial reps. Cutting the range short inflates the load and the estimate.
- Don't compare with a squat. I found no source that turns a leg press max into a squat max, so this page doesn't.
The Reynolds equation is safest for 1RMs inside the range of the 20 people used to cross-validate it, which was 133.9 to 469.6 kg (295 to 1035 lb)[1]. The calculator warns you when its estimate falls outside that.
Using the Rep Table
The results include a table of loads for 1 to 10 reps. It runs each equation backwards from its own 1RM and averages them, so the row for your own set returns the weight you entered.
This reverse use is my arithmetic. The equations were tested for predicting a 1RM from a set, and I found no study that checks the loads you get the other way. Treat the table as a starting point and confirm it with a real set.
For a measured reference, Reynolds found the mean load on a plate-loaded leg press was 85.91% of 1RM for 5 reps, 70.1% for 10 reps and 51.58% for 20 reps[1]. These are means for 90 people (the 70 plus the 20 cross-validation subjects) on one machine.
For general training, ACE cites the American College of Sports Medicine's advice of at least one set of 8 to 12 reps at a challenging weight, which it puts at about 60 to 70% of 1RM[5].
Getting a Set You Can Trust
- Go to failure with clean reps. The equations assume you stopped because you couldn't do another full rep. If you stopped early, the result reads low.
- Pick a heavier, lower-rep set. A 5RM predicted better than a 10RM or 20RM in Reynolds' data[1]. They didn't test 3, 4 or 6 reps, so a set near 5 is the best-supported choice.
- Rest long enough. Reynolds urged a 5-minute rest between sets in rep-max testing, arguing that shorter rests are likely too short[1].
- Repeat it the same way. Same machine, same foot position, same tempo and the same way of counting the load.
I found no source for machine-specific safety rules, such as how to set the safety stops, so follow the manufacturer's instructions and ask a qualified coach if you are unsure.
Leg Press Strength Standards
I looked for leg press norms I could check. Brown and Miller (1998) built percentile tables from 304 women aged 20 to 70+, and concluded that the American College of Sports Medicine's leg press norms for women looked too low[6]. I could only read the abstract, not the tables.
I did not find a men's table I could verify, and norms depend on the machine. Some sites publish beginner-to-elite tables, but I could not trace their numbers to a study. So the page doesn't grade you.
If you add your body weight, the page shows your 1RM divided by it as a plain ratio. It is useful for tracking your own change over time, and it is not a rating.
What I Removed From the Old Version
The earlier version of this calculator carried numbers and claims I couldn't trace to a source I could open. I left them out:
- Machine-type multipliers. The old calculator adjusted the result by machine style. I found no study that gives such factors, and Reynolds advises against using his equations on other machines[1].
- Strength-level labels and standards tables. No verifiable source, as above.
- A claim about 45-degree machines. The old page cited a 2024 paper on leg press muscle activity. From its abstract, it compares outdoor and gym machines in trained young men, not machine angle and force[7].
- Programming tables and rest-day advice. I found no source for the specific numbers.
- An unexplained average. The old page defaulted to "Average of All Formulas" and didn't say which equations went into it. Brzycki, Lander and O'Connor read low on the leg press in Reynolds' test[1], so any average that leans on them may read low too. That is my inference, not something a study tested.
Things I couldn't verify: Kemmler's leg press tables, Reynolds' published %1RM equation by rep count, and any strength norms for the leg press.
For other rep-max tools, see the One Rep Max Calculator, the 5 Rep Max Calculator and the 10 Rep Max Calculator.
Frequently Asked Questions
Sources & References
- Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Reynolds JM, Gordon TJ, Robergs RA. Journal of Strength and Conditioning Research 20(3):584-592 (2006)
- Predicting maximal strength in trained postmenopausal woman. Kemmler WK, Lauber D, Wassermann A, Mayhew JL. Journal of Strength and Conditioning Research 20(4):838-842 (2006)
- The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. Journal of Strength and Conditioning Research 11(4):211-213 (1997)
- Validity of 1RM prediction equations for older adults. Knutzen KM, Brilla LR, Caine D. Journal of Strength and Conditioning Research 13(3):242-246 (1999)
- Weight Training Load Calculator. American Council on Exercise. ACE Fitness, Tools & Calculators (web page, undated; it cites ACSM Guidelines, 11th ed., 2022)
- Normative data for strength and flexibility of women throughout life. Brown DA, Miller WC. European Journal of Applied Physiology and Occupational Physiology 78(1):77-82 (1998)
- Comparative electromyographic analysis in leg press of traditional fitness equipment, traditional outdoor fitness equipment, and a new model of outdoor fitness equipment in trained young men. Abelleira-Lamela T, Marcos-Pardo PJ, Abraldes JA, González-Gálvez N, Espeso-García A, Esparza-Ros F, Vaquero-Cristóbal R. Applied Sciences 14(16):7390 (2024)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.