Skip to content
BarWeight
Tools

How we calculate

By

Every figure here is computed by us or quoted from a cited source. We do not test gear. How we know this.

Every number on this site can be checked by hand. Here is where each one comes from.

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.

The method, applied

What a spec-read product card looks like

Everything above describes how a number gets onto this site. This is that method applied to a retail listing: published specs only, the date they were read, no price, no rating, and an explicit list of the things you still have to check yourself before ordering.

BarWeight is a participant in the Amazon Services LLC Associates Program. We earn a commission from qualifying purchases made through links on this page, at no extra cost to you. Full disclosure.

One card, as an example

Cap Pro Series 7 ft Olympic Barbell

B006R4EOWI
BarbellsCAP Barbell7 ft
Length
7 ft
Sleeve
2 in Olympic

A nominal 45 lb bar — the size it is sold and stamped as, which is the exact distinction this page exists to make. We have not weighed it.

Best for: A general-purpose 7 ft bar for a rack-and-plate home gym.

Skip if: You want a specific knurl or tensile rating — the listing does not publish those figures.

Check these yourself before ordering

  • — The actual bar weight, which the listing title does not state
  • — Shaft diameter and whether there is a centre knurl
  • — Loadable sleeve length against how many plates you own
View on Amazon

Specs read from the listing on 2026-07-24. Listings change — confirm the current spec and option before you order.

The same method across the whole category is on how to choose a barbell, and the commercial arrangement behind it is spelled out on the affiliate disclosure.

Questions about the method

▶Have you tested any of the equipment you link to?

No, and we will not say otherwise. We do not own this equipment, we have not lifted on it, and we have not measured it. Every figure on a product card was read off that product's own listing or manufacturer spec sheet on the date printed at the bottom of the card. That is why there are no star ratings, no scores and no "our testers found" language anywhere on this site. Where a seller did not publish a spec, the field is left blank rather than estimated, and a product is simply not eligible for a recommendation that depends on the spec it did not publish.

▶Where do the bar and plate weights come from?

The 20 kg and 15 kg bars are competition specifications taken from the IWF Technical and Competition Rules and Regulations. Kilo disc colours are the same IWF specification. Pound-denominated bars are nominal American gym sizes — the size a bar is sold and stamped as, not a weight anybody put on a scale — and pound plate colours are a manufacturer convention rather than a standard. We do not own a certified scale and we do not pretend to. Manufacturing tolerance is real, so if the exact figure matters to your training log, weigh your own bar.

▶Which one-rep max formula should I use?

We show 4 published equations separately rather than blending them into a house number, because they genuinely disagree and hiding that would be dishonest. They diverge most above about five reps, so a max estimated from a heavy triple is far more useful than one estimated from a set of twelve. The midpoint we display is a plain arithmetic mean of the 4, labelled as a midpoint, and it carries no authority the individual equations do not. An estimated max is a programming input, not a number to chase.

▶How does the plate solver decide which plates to use?

One equation: plates per side equals the target minus the bar, divided by two. The solver then fills each side heaviest plate first from the set you tell it you own, never exceeding the target. For any standard plate set that greedy fill is provably optimal. For an unusual custom set it can theoretically miss, so when the greedy pass leaves a gap and the search space is small enough, the solver also runs a bounded exhaustive search and keeps whichever result lands closer. When your target is not buildable at all, the tool says so and reports the shortfall instead of quietly rounding to something you did not ask for.

▶How does BarWeight make money, and does it change the numbers?

The calculators are free and carry no logins and no paywall. The site earns through Amazon affiliate links on the equipment cards — we are paid a percentage of qualifying purchases, at no extra cost to you. It cannot change what a calculator tells you, because the calculators are arithmetic covered by a test suite of hand-computed cases: if the math changed, the build would fail. It does not change which products appear either, because the 180 products on this site are the ones whose listings we were able to verify, and the recommendations are driven by published specs rather than by commission.