STRENGTH CALCULATORS
Three free lifting calculators — no sign-up, no email. Estimate a one-rep max from a set you actually did, work out exactly which plates go on the bar, and turn an RPE into a percentage of your 1RM.
These are the same calculations Cornerstone Strength runs behind every set you log. Here they're free to use on their own.
A CALCULATOR ANSWERS ONE SET
A number on its own doesn't tell you what to do next week. In the app every set you log feeds the next decision — your max updates itself, the plan adjusts to it, and you can see whether any of it is working.
FREQUENTLY ASKED QUESTIONS
Are these strength calculators free?+
Yes — all three are free, with no account, no email, and no cap on how often you use them. They run in your browser; nothing you type is sent anywhere or stored.
Which lifting calculator do I need?+
Use the 1RM calculator when you want your max from a set you actually did, and the percentages to program from. Use the plate calculator when you know the weight and need to know what to load. Use the RPE chart when you want to pick a weight from how hard the set should feel rather than a fixed percentage.
How accurate are strength calculators?+
It depends which one. Plate loading is exact arithmetic. A one-rep max estimated from a heavy set of five reps or fewer is usually within a few percent of a true max, and gets looser as the reps climb. RPE-to-percentage varies by lifter, exercise, and day — treat it as a starting point you adjust from, which is the point of auto-regulation.
Do these calculators work in kg as well as lb?+
Yes. The plate calculator and RPE chart both switch between pounds and kilograms, including the standard lb and IPF kg plate colours. The 1RM calculator is unit-agnostic — enter your numbers in either unit and the estimate comes back in the same one.
Can I get these numbers without doing the math every session?+
That's what the app is for. Cornerstone Strength updates your estimated 1RM from every set you log, prescribes working weights as percentages of it, and shows the target on the set in front of you — so the calculation happens before you pick up the bar, not after.
TRAIN WITH THE FULL APP
Cornerstone Strength turns these calculations into your training — your estimated max updates from every set, working weights come prescribed as percentages of it, and the reasoning comes with them. Log the lift; we'll handle the math.
