Strength

Leg Press Calculator

Updated 1 Nov 2026 · Source: Epley, Brzycki and Lombardi formulas ↗

Enter the plates you loaded on the sled and the reps you finished. The calculator estimates your one rep max on that same machine and builds a percent chart from it.

Worked example

Epley: 360 × (1 + 10 ÷ 30) = 480.0 lb
Brzycki: 360 × 36 ÷ (37 − 10) = 480.0 lb
Lombardi: 360 × 10^0.10 = 453.2 lb
Average of the three: (480.0 + 480.0 + 453.2) ÷ 3 = 471.1, shown as 471 lb

Percent chart for a 471 lb max

% of max	Weight (lb)	Reps you might get
100%	471	1
95%	448	about 2
90%	424	about 3
85%	400	about 5
80%	377	about 7
75%	353	about 10
70%	330	about 12
65%	306	about 14
60%	283	about 16
55%	259	about 19
50%	236	about 21

Count the plates, then note the machine

The input is the plates only. The empty sled has its own weight, often about 75 to 125 lb and sometimes more, so check the label on your machine.

You can add the sled to your number or leave it out, but do the same thing every time. With the default set of 360 lb for 10 reps, the estimate is about 471 lb of plates. If you also counted a 100 lb sled, every number on the page would shift up.

What a 45 degree sled really puts on your legs

On a sled that rides up a slope, only part of the weight pushes back along the rails. That part equals the loaded weight times the sine of the rail angle; the rest presses into the rails. At 45 degrees the sine is about 0.707, so you push about 71% of plates plus sled.

Take 360 lb of plates on a 100 lb sled. That is 460 lb loaded, but only about 325 lb acts along the slide. Friction in the rollers takes off a little more, and no one has a fixed figure for it. A sled set at a different angle gives a different share.

Why a leg press number does not convert to a squat

Besides the angle, the machine does a lot of work a squat leaves to you. Your back rests on a pad, the sled runs on a fixed track, and nothing has to be balanced over your feet. How deep you go also depends on the seat setting.

Put together, there is no fair ratio between the two lifts, and a big leg press says little about your squat. If you want a squat max, test a set of squats and run it through the squat max calculator.

Mistakes that skew the estimate

The last point matters most. A heavier set of 3 to 8 reps gives a tighter estimate, and the 1 rep max formula page shows how far apart the formulas get as reps climb.

Moving the seat or foot position between test days.
Counting short reps that stop well above your usual depth.
Adding the sled weight one week and not the next.
Testing with sets above 10 to 12 reps, where the formulas drift apart.

Putting the estimate to work

Because the number belongs to one machine, use it only on that machine. Pick a percent from the chart under the calculator to set your working sets, then retest with a fresh set every few weeks to keep the loads current.

Before heavy sets, set the safety stops so the sled cannot come down past a depth you can push out of. For a broader view of how weights map to reps, see the 1 rep max chart.

Dumbbell Bench Max Calculator, Bench Press Calculator, FFMI Calculator, Powerlifting Calculator

Questions

Does the calculator add the sled weight?

No. It works with whatever number you type in. Enter plates only or plates plus sled, and keep that choice for every test.

Can I compare my leg press with someone at another gym?

Not fairly. Sled weight, rail angle and friction all differ between machines, so the same plates can feel very different.

Is a set of 20 reps fine for estimating a max?

It gives a rough number at best. Estimates get less accurate above about 10 reps, so a heavier set is a better test.

How we calculate: every formula, with its author and year, is on our method page; data sources and their licenses are on sources.

gymnical.com gives estimates from published formulas and public data. It is not medical advice and not a training prescription. Last reviewed November 2026.