The total weight on a leg press equals the sled (carriage) weight plus whatever plates you load onto it. If the sled weighs 100 lbs and you add 200 lbs in plates, you’re pressing 300 lbs. But the actual force your legs experience can be lower than that number, depending on the type of machine you’re using.
Start With the Sled Weight
Every leg press has a moving carriage, or sled, that weighs something even before you add a single plate. This starting weight varies widely by brand and model. A Rogue Iso Leg Press, for example, has a sled weight of 182 lbs. Other commercial machines range anywhere from 70 lbs to over 120 lbs, with some heavy-duty models going higher. There’s no universal standard.
To find your machine’s sled weight, look for a label or sticker on the frame, usually near the base or on the side of the carriage. If there’s nothing visible, search the manufacturer’s name and model number online. Most brands list the sled weight in their product specs. If you’re at a commercial gym, the front desk staff or a trainer may know, or you can check the brand’s website directly.
Add Up the Plates
Most commercial gym leg presses use Olympic plates with a 2-inch center hole. The most common sizes in pounds are 2.5, 5, 10, 25, 35, and 45 lbs. In kilograms, you’ll typically see 1.25, 2.5, 5, 10, 15, 20, and 25 kg plates. Count the plates on each side, multiply by two (since both sides are loaded equally), and add that to your sled weight.
For example: three 45-lb plates on each side gives you 6 × 45 = 270 lbs in plates. Add a 100-lb sled and your total load is 370 lbs. One thing worth knowing: cheap plates can be surprisingly inaccurate. A plate stamped “45 lbs” might actually weigh anywhere from 40 to 50 lbs. Variations of 10% or more have been documented, with extreme cases where a “45-lb” plate weighed as little as 38 lbs or as much as 59 lbs. For most people this doesn’t matter much, but if precision matters to you, a bathroom scale can settle the question.
Why the Angle Changes What You Actually Lift
Here’s where it gets interesting. The most popular leg press design, the 45-degree angled sled, doesn’t make you push the weight straight up against gravity. You’re pushing it along a track set at an angle. Physics reduces the effective load because only a portion of the weight works against gravity.
The formula is simple: multiply the total weight by the sine of the track angle. For a true 45-degree leg press, sin(45°) is approximately 0.707. So if you load 400 lbs total (sled plus plates), the actual resistance your legs feel is closer to 400 × 0.707 = 283 lbs. That’s roughly 70% of the loaded weight. In practice, friction between the sled and the rails eats up some additional force, so real-world estimates often land between 50% and 70% of the total load, depending on the machine’s condition and design.
Horizontal leg presses that use a cable-and-pulley system work differently. A 1:1 pulley ratio delivers close to the full weight you select on the stack. A 2:1 ratio cuts the felt resistance roughly in half. Most selectorized (pin-loaded) leg presses note their ratio in the manual or on the machine itself.
What to Log in Your Training Journal
For tracking progress, consistency matters more than calculating exact effective force. Pick one method and stick with it. You have two practical options:
- Total load: Record sled weight plus plate weight (e.g., “370 lbs”). This is the better choice if you switch gyms or machines regularly, because it lets you compare numbers across different equipment.
- Plates only: Record just the plate weight (e.g., “270 lbs”) and note which machine you used. This works fine if you always train on the same leg press.
Even though the effective load on your legs is technically less than the number you write down (due to the angle), that doesn’t matter for tracking. What matters is that when you go from 270 lbs in plates to 315 lbs in plates on the same machine, you got stronger. The relative change is real regardless of how you label it.
Comparing Across Different Machines
A “400-lb leg press” on one machine is not the same as 400 lbs on another. A 45-degree sled press at 400 lbs delivers roughly 280 lbs of effective resistance. A vertical leg press at 400 lbs delivers close to the full 400 lbs because you’re pushing straight against gravity. A horizontal cable machine at 400 lbs could deliver anywhere from 200 to 400 lbs depending on its pulley ratio.
This is why leg press numbers don’t translate directly to squat or deadlift strength, and why comparing leg press numbers between people who use different machines is mostly meaningless. If someone tells you they leg press 800 lbs, the machine type matters enormously. On a 45-degree press, their legs are handling roughly 565 lbs of effective force. On a vertical press, it’s the full 800.
For your own training, the simplest approach is to find the sled weight of your specific machine once, write it down somewhere accessible, and then just count plates each session. Over time, the only number that truly matters is whether it’s going up.