It is a basic physics problem depending on the placement and the size and angle of the pulleys will determine to what factor the pulleys are reducing the load. There is probably a simple equation based on those measurments.

Yea thats the problem with going to different gyms. Not only are the cable machines different, but the free weights and plates are also at different weights. 45 at the high school weight room feels like 25, and 45 at LA Fitness feels like 55. I can't tell what's accurate and what's not. Not only that, when I sneak some weights into the locker room to weigh them, every scale is different too! wtf

Machines are totally unreliable. Not only are the angles of each machine slightly different, so is the amount of friction in each mechanism. Finally, the numbers on the weights in the machine sometimes don't seem to relate to the actually weight. Sometimes I think its just a number.

Freeweights can be unreliable too, and can mislead you when it comes to knowing how much you're lifting.

Just to top it all off, scales can be old, poor quality or not set up correctly (eg placed on a soft surface like carpet) so they can't always be relied on to give you a proper reading.

One is kilos and one is lbs. I bet big $ on that.

Maybe, but the labels are the exact same on the weights, and they look to be about the same size. Although the comparision in what felt the same was about the same or a little bit more (80 on one machine vs 150 on the other one)