There is no one weight plate size. Competition plates follow a colour code: 25 kg red, 20 blue, 15 yellow, 10 green, 5 white. Olympic plates of 10 kg and up are 450 mm across. Gym plates vary, so RIGOR assumes a rack of 25 down to 1.25 kg, or 45 down to 2.5 lb.
What are the weight plate sizes in kg and lb?
A gym's plates come in a handful of weights, and the plate calculator's rack is the quickest list of them. RIGOR is the app behind this guide, and it starts a commercial gym with a full rack: eight of the biggest plate and four of every smaller size. Whether a gym really has those is for its own rack to say.
| Unit | Plate sizes | How many |
|---|---|---|
| Kilograms | 25, 20, 15, 10, 5, 2.5, 1.25 kg | Eight 25 kg, four of each other |
| Pounds | 45, 35, 25, 10, 5, 2.5 lb | Eight 45 lb, four of each other |
The two lists are separate and the app never converts one into the other. The pound rack has no 20 or 15 and the kilogram rack has no 35. The barbell plate calculator loads any weight from the rack, and how the plates add up is the sum behind it.
What do the colours of kg plates mean?
They are a code for weight, set by the weightlifting federation for competition plates. Wikipedia's Barbell article prints it as the code the International Weightlifting Federation requires. The federation's own rulebook could not be opened, since its site refuses requests, so this table is that article's reading of it.
| Colour | Weight |
|---|---|
| Red | 25 kg |
| Blue | 20 kg |
| Yellow | 15 kg |
| Green | 10 kg |
| White | 5 kg |
| Red | 2.5 kg |
| Blue | 2 kg |
| Yellow | 1.5 kg |
| Green | 1 kg |
| White | 0.5 kg |
Wikipedia adds that outside competition, plates "need not conform to IWF or powerlifting specifications, and can be of any colour." A black iron plate says nothing by its colour. Read the number.
RIGOR is a strength training app for iPhone that builds your plan and sets every weight by rules you can read.
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How big is a weight plate?
It depends on the weight, the maker and the rule. The one fixed number is the top: Wikipedia gives Olympic plates of 10 kg and up as 450 millimetres (18 in). Smaller plates need not be that big.
| Source | What it says |
|---|---|
| Wikipedia, Barbell | Olympic plates of 10 kg and up: 450 mm (18 in) |
| Titan, 45 lb cast iron | 454 mm (17.875 in) across, 34 mm wide |
| Rogue, 20 kg and 25 kg | Both 442 mm across |
Rogue's 20 and 25 kg plates are 442 mm across, under the 450 mm Wikipedia gives for Olympic plates, while Titan's 45 lb plate is 454 mm. So a plate's weight does not fix its width. For a rack, the fit that matters is the hole and the bar, in the next section.
Do all plates of one weight weigh the same?
Not exactly. A 45 lb plate is about 20.4 kg (45 × 0.4536), and a 225 lb bar is 45 + 4 × 45 = 225 lb, about 102.1 kg, not 100. Titan lists a weight tolerance of plus or minus 3% for its 45 lb plate, and Rogue lists the same for its Olympic plates in kilograms. That is up to about 1.35 lb either way on a 45.
For training a steady error cancels if you load the same way each time. RIGOR compares each exercise only with its own history, so a Smith machine lift is never measured against its free-bar version.
What is the difference between Olympic and standard plates?
The hole. Olympic plates have a 2 inch centre hole and fit the sleeve of an Olympic bar. Titan's 45 lb plate has a 50.5 mm opening. Standard plates fit a bar of about one inch: Wikipedia gives centre holes of 27 to 31 mm.
RIGOR treats the 1-inch bar as the exception: it gives that bar its own plates, 20, 10, 5, 2.5 and 1.25 kg in a kilogram gym and 25, 10, 5 and 2.5 lb in a pound gym. Every other bar uses the main rack above. Plates smaller than those, such as fractional plates, are added in gym setup.
Wikipedia warns that standard plates vary and "may prove very problematic if plates are mixed and matched".
When does this not apply?
This page is equipment, so no training study applies. The colour code from Wikipedia's reading of the IWF, and the plate measurements from the maker pages listed under sources.
RIGOR starts from a full rack, then yours
Questions
What is the standard size of a weight plate?
There is none for gym plates. Olympic plates of 10 kg and up are 450 mm across. Smaller plates are smaller, and makers differ: Rogue's 20 kg and 25 kg plates are 442 mm across.
Do all 45 pound plates weigh the same?
Not exactly. Titan lists plus or minus 3% for its 45 lb plate, which is up to about 1.35 lb either way.
Are standard weight plates 1 inch?
Standard plates fit a bar of about one inch, with centre holes of 27 to 31 mm according to Wikipedia. Olympic plates have a 2 inch hole, 50.5 mm on Titan's 45 lb plate.
What are the common sizes of gym plates?
In kilograms 25, 20, 15, 10, 5, 2.5 and 1.25. In pounds 45, 35, 25, 10, 5 and 2.5. Those are the plates RIGOR starts a gym with, and a gym may lack some or have others.
Is a 20 kg plate the same as a 45 lb plate?
Close but not equal. 45 lb is about 20.4 kg, so a 225 lb bar is about 102.1 kg, not 100 kg. RIGOR keeps a kilogram gym and a pound gym apart and does not convert one into the other.
