THE TAKEAWAY

Multiply your max by the requested percentage, then check what your bar and plates can actually load.

The calculation is simple

A percentage expresses a training load relative to a one-rep maximum. For a 100 kg max, 80% is 80 kg. Percentages provide a common language, but the number of reps someone can perform at the same percentage can vary.

Sources: NSCA: Intensity or resistance

Exact versus rounded

Suppose your estimate is 137 kg and your plan calls for 75%. The exact result is 102.75 kg. IronMath Fitness’s percentage table rounds kg results to the nearest 2.5 kg, giving 102.5 kg. In pounds it uses 5 lb increments.

Those increments are defaults, not a promise that your gym has the right plates. A different bar, missing change plates, or limited plate quantities can change what is possible.

Check the whole loading system

  • Use the max for the exercise you are about to train.
  • Confirm whether your plan uses a measured, estimated, or deliberately reduced training max.
  • Check your bar weight and available plates.
  • Write down the actual weight you used, including any rounding.

Avoid false precision

A calculator can give a decimal answer even when the underlying max is an estimate. Keep the program’s purpose in mind instead of treating a small decimal difference as a meaningful change in strength.

When your recent performance changes, review the estimate and your plan rather than automatically applying an old number forever.

Sources: NSCA: Intensity or resistance

PUT IT INTO PRACTICE

Check your own numbers.

Open calculator

Sources & approach

This guide combines linked references with IronMath Fitness examples. It provides general information, not a personal training plan.