A red spring is not a single weight.

You already read the body in front of you: how it moves, where it strains, what your cue changes. But a Pilates spring does not load like a dumbbell, and the resistance your client actually meets shapes everything you watch for. The free Spring Load Calculator shows you how springs really load, so what you see starts to make sense.

How spring load changes as the carriage moves: a spring’s force grows with how far it is stretched. At the start of a stroke the carriage sits near the stopper and the spring is close to its resting length, so the load is light. As the carriage travels out the spring stretches and the load climbs, and it is heaviest at full extension. A tall client who pushes the carriage further works a heavier red spring than a shorter client on the same setting, which is why the same color is not the same workout.

Pick a brand, choose a spring color, and drag through the stroke to read the load at any point. Springs from six brands are included, because a red spring on one reformer is not a red spring on another.