How we calculate

Plate math

One equation: plates per side = (target − bar) / 2. The solver fills each side heaviest plate first from the set you say you own, never exceeding the target. For any standard plate set that greedy fill is optimal. For an unusual custom set it can theoretically miss, so when the greedy pass leaves a gap and the search space is small the solver also runs a bounded exhaustive search and keeps whichever result gets closer.

When your target is not buildable the tool says so and reports the shortfall rather than rounding silently.

Units

One pound is exactly 0.45359237 kilograms, by the 1959 international yard and pound agreement. That exact constant is used in every conversion on the site. We never use 2.2 or 0.454.

One-rep max

Four published equations, reproduced as published, each shown separately rather than blended into a house number:

• Epley — 1RM = w x (1 + r / 30). Epley, B. (1985). "Poundage Chart." Boyd Epley Workout. Lincoln, NE: Body Enterprises.
• Brzycki — 1RM = w x 36 / (37 - r). Brzycki, M. (1993). "Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue." Journal of Physical Education, Recreation & Dance, 64(1), 88-90.
• Lombardi — 1RM = w x r^0.10. Lombardi, V. P. (1989). Beginning Weight Training: The Safe and Effective Way. Dubuque, IA: Wm. C. Brown.
• O'Conner — 1RM = w x (1 + 0.025 x r). O'Conner, B., Simmons, J., & O'Shea, P. (1989). Weight Training Today. St. Paul, MN: West Publishing.

The midpoint we display is a plain arithmetic mean of those four, labelled as a midpoint. It is not a fifth formula and it carries no authority the others do not. The percent-of-max table is derived by inverting the Epley equation, which is stated on the page where it appears.

Bar and plate weights

The 20 kg and 15 kg bars are competition specs from the IWF Technical and Competition Rules & Regulations. Pound-denominated bars are nominal American gym sizes — the size a bar is sold and stamped as. Kilo disc colours are the IWF competition specification; pound plate colours are a manufacturer convention and not a standard.

None of these are weights we measured. We do not own a certified scale and we do not pretend to. Manufacturing tolerance varies. If the exact figure matters to you, weigh your bar.

What we will not do

• Claim we tested equipment we have not tested.
• Publish a rating, price, or review count we did not derive from something real.
• Invent a formula or present an estimate as a measurement.
• Give medical advice. Nothing here is a substitute for a professional who can watch you lift.

Corrections

If a number here is wrong, it is a bug and we want it. The calculators are covered by a test suite of hand-computed cases, so a reported error becomes a failing test before it becomes a fix.