u/rubberbandsapp

Anyone who trains with loop bands has hit this: you need something between your red and your black, so you stack, and then you have no idea what you are actually pulling.

I built a small web calculator for it. No sign-up, no app install, works fine on a phone.

What it does:

• Tick up to 4 bands and it gives you the combined resistance, in lbs or kg.
• Type in a resistance you are aiming for and it ranks the three closest combinations you can make from your set.
• Loads presets for common sets (Serious Steel, Clench, X3, Undersun, Harambe, Bodylastics tubes), or you can type a brand name or paste a product URL and it will go look up the specs.
• Whatever set you end up with gets saved in your browser so you are not re-entering numbers every time. You can bookmark it and use it as a reference guide.
• Handles tube bands with handles too, which carry one printed rating instead of a range. Although the math with tubes is much more straightforward.

Note: stacking is only clean arithmetic when the bands are the same length. So if you stack a 41 inch band with a 34 inch one they are at different percentages of their length and the real total lands somewhere inside the range rather than at the top of it. Same length bands stack predictably. Mismatched ones give you a ballpark, not a number.

Link: https://rubberbands.app/calculators/band-resistance

Disclosure so nobody has to dig: I make a resistance band training app, and this is on that site. The calculator is free, and there is no account or email gate on it. There are a few others on there as well (1RM, TDEE, body fat by the Navy tape method) but the band one is the one I really wanted to make.

The part I would like feedback on is the band library. If your set is not in the presets and the lookup gets your numbers wrong, tell me the brand and length and I will get it in there and fix it. I think it's a pretty cool tool.