Weight Plate Dimensions: Diameter, Thickness and Hole Size
For lifters fitting plates to a bar, rack or storage tree, and for anyone checking whether a plate is Olympic or standard. Diameters, thicknesses and hole sizes for iron, bumper and calibrated plates, in pounds and kilograms.
A full-size Olympic weight plate (45 lb, 20 kg or 25 kg) is 450 mm (17.72 in) in diameter with a center hole of about 50.4 mm (1.98 in) to fit a 50 mm (2 in) bar sleeve. Thickness depends on the material: about 2 in (50 mm) for a cast iron 45 lb plate and 2.2 to 3.3 in (55 to 83 mm) for a rubber bumper.
- Full-size diameter
- 450 mm (17.72 in)
- Olympic hole
- 50.4 mm (1.98 in)
- Standard hole
- 27-31 mm (about 1 in)
- Bar height on 450s
- 225 mm (8.86 in)
On this page
- Olympic weight plate sizes at a glance
- 45 lb plate dimensions
- 20 kg plate dimensions (and the other kilo plates)
- Cast iron plate diameter and thickness
- Bumper plate dimensions and thickness
- Weight plate hole sizes: Olympic vs standard
- Olympic plate colors (IWF and IPF code)
- How many plates fit on a bar
- Why the full-size diameter matters
- Checking an unknown plate
- Frequently asked questions
Olympic weight plate sizes at a glance
Two numbers are shared by almost every plate made for a 7 ft Olympic bar: the 450 mm outer diameter of the big plates and the 50 mm sleeve they slide onto. Everything else, including thickness and the size of smaller plates, depends on the brand and material.
| Plate type | Diameter | Thickness of the 45 lb / 20 kg | Center hole |
|---|---|---|---|
| Olympic cast iron | 450 mm (17.72 in) for 45 lb; smaller plates shrink | About 50 mm (2 in) | 50-51 mm (2 in) |
| Training bumper (rubber) | 450 mm (17.72 in) for 10 lb and up | About 83 mm (3.25 in) | 50-51 mm (2 in) |
| Competition bumper | 450 mm (17.72 in) for 10 kg and up | About 55 mm (2.15 in) | 50-51 mm (2 in) |
| Calibrated steel (powerlifting) | 450 mm for 20 kg and up; smaller below | Roughly 1 in (about 22-27 mm) | 50-51 mm (2 in) |
| Standard (1-inch) iron | Varies; smaller than Olympic | Varies | 27-31 mm (1.06-1.22 in) |
The calibrated steel thickness is a typical range across brands; Rogue does not publish a thickness for its calibrated plates. The bumper and iron figures come from Rogue's published specs, detailed in the tables below.
45 lb plate dimensions
A 45 lb plate weighs 20.41 kg and is the pound-system equivalent of the 20 kg plate. Its diameter is 17.72 in (450 mm) on most modern plates; older or budget iron plates run from about 17.5 to 17.75 in.
Thickness is where 45s differ most. A dense competition bumper is 2.15 in thick, a training bumper 3.25 in, and a cast iron plate about 2 in. That difference decides how many plates fit on the bar (see the loading table further down).
20 kg plate dimensions (and the other kilo plates)
In kilogram gyms the full-size plates are 25 kg and 20 kg, both 450 mm across. The IWF requires all discs of 10 kg and heavier to be 450 mm in diameter, plus or minus 1 mm. Calibrated powerlifting plates, which are thin steel, only reach full size at 20 kg.
| Plate | Weight in lb | Diameter (mm) | Diameter (in) |
|---|---|---|---|
| 50 kg | 110.23 lb | 450 | 17.72 |
| 25 kg | 55.12 lb | 450 | 17.72 |
| 20 kg | 44.09 lb | 450 | 17.72 |
| 15 kg | 33.07 lb | 400 | 15.75 |
| 10 kg | 22.05 lb | 325 | 12.80 |
| 5 kg | 11.02 lb | 228 | 8.98 |
| 2.5 kg | 5.51 lb | 190 | 7.48 |
| 1.25 kg | 2.76 lb | 160 | 6.30 |
| 0.5 kg | 1.10 lb | 134 | 5.28 |
| 0.25 kg | 0.55 lb | 112 | 4.41 |
All of these have a 50.4 mm hole. Smaller steel plates from other brands land within roughly 10 mm of the figures above, because the steel volume needed for each weight is the same.
Cast iron plate diameter and thickness
Iron plates get smaller as they get lighter, so only the 45 lb (and 100 lb) plates are full size. Rogue's Deep Dish plates are a representative current design:
| Plate | Diameter | Thickness |
|---|---|---|
| 100 lb (45.36 kg) | 450 mm (17.72 in) | 75 mm (2.95 in) |
| 45 lb (20.41 kg) | 450 mm (17.72 in) | 50 mm (1.97 in) |
| 35 lb (15.88 kg) | 360 mm (14.17 in) | 34.5 mm (1.36 in) |
| 25 lb (11.34 kg) | 276 mm (10.87 in) | 34.5 mm (1.36 in) |
| 10 lb (4.54 kg) | 229 mm (9.02 in) | 20 mm (0.79 in) |
| 5 lb (2.27 kg) | 190 mm (7.48 in) | 14.5 mm (0.57 in) |
Other brands' 2.5 lb iron plates are typically about 6 to 7 in (15 to 18 cm) across. Many iron plates have a dished face or a raised hub, so the thickness at the rim and at the hole can differ by several millimeters. If you are fitting plates to a storage peg or a short sleeve, measure the thickest point, which is usually the hub.
Bumper plate dimensions and thickness
Bumper plates are rubber or urethane plates designed to be dropped. Every bumper from 10 lb (or 10 kg) up is 450 mm across, so the plate, not the bar, hits the floor. Rubber is far less dense than iron, so bumpers are much thicker.
| Plate | Training bumper (Rogue HG 2.0) | Competition bumper (Rogue) |
|---|---|---|
| 10 lb (4.54 kg) | 1.00 in (25.4 mm) | Not made |
| 15 lb (6.80 kg) | 1.37 in (34.8 mm) | Not made |
| 25 lb (11.34 kg) | 2.00 in (50.8 mm) | 1.25 in (31.8 mm) |
| 35 lb (15.88 kg) | 2.75 in (69.9 mm) | 1.70 in (43.2 mm) |
| 45 lb (20.41 kg) | 3.25 in (82.6 mm) | 2.15 in (54.6 mm) |
| 55 lb (24.95 kg) | 3.75 in (95.3 mm) | 2.50 in (63.5 mm) |
Competition bumpers have a steel or iron insert, which is why they are about a third thinner than training bumpers of the same weight. Kilogram competition sets follow the same pattern: a 25 kg disc is in the region of 2.5 in (63 mm) thick and a 10 kg disc around 1.2 in (30 mm), with small differences between brands. IWF rules fix the diameter, not the thickness.
10 lb and 15 lb bumpers are only 1 to 1.4 in thick. Dropped alone or as the only plate on the bar, they can bend or crack. Use them with heavier bumpers on the outside, or keep drops controlled.
Weight plate hole sizes: Olympic vs standard
- Olympic plates: the hole is about 50 to 51 mm (1.97 to 2.01 in). Bar sleeves are 50 mm (1.97 in), and the hole is machined a little larger so plates slide on and off. Rogue quotes 50.4 mm ± 0.1 mm.
- Standard plates: made for 1 in bars, with holes of roughly 27 to 31 mm (1.06 to 1.22 in). The bars themselves are 25 to 29 mm thick.
- Dumbbell plates: spinlock dumbbell handles are usually 25 mm, 28 mm or 30 mm across, so dumbbell plates use the standard-size hole. Check the handle diameter before mixing brands.
An Olympic plate will slide onto a standard bar but rattle around the 1 in shaft and rest off center, which is unsafe. A standard plate will not fit an Olympic sleeve at all. Sleeve adapters exist that convert a 1 in bar to 2 in; they work for light dumbbell or curl-bar use, not for heavy barbell lifts. See the barbell size guide for bar and sleeve dimensions.
Olympic plate colors (IWF and IPF code)
Competition plates use a fixed color code so judges and loaders can read the bar at a glance. Many training plates copy it.
| Weight | Color | In pounds |
|---|---|---|
| 25 kg | Red | 55.12 lb |
| 20 kg | Blue | 44.09 lb |
| 15 kg | Yellow | 33.07 lb |
| 10 kg | Green | 22.05 lb |
| 5 kg | White | 11.02 lb |
| 2.5 kg | Red (small) | 5.51 lb |
| 2 kg | Blue (small) | 4.41 lb |
| 1.5 kg | Yellow (small) | 3.31 lb |
| 1 kg | Green (small) | 2.20 lb |
| 0.5 kg | White (small) | 1.10 lb |
Pound-denominated colored bumpers usually map 55 lb to red, 45 lb to blue, 35 lb to yellow, 25 lb to green and 10 lb to black or white, but this is a convention, not a rule. Powerlifting sets often add a 50 kg plate (some federations allow it), and IPF rules allow plates of 10 kg and under to be any color.
How many plates fit on a bar
The loadable sleeve of a men's Olympic bar is roughly 16 to 16.5 in long (Rogue's Ohio Bar: 16.40 in, 417 mm). Divide that by plate thickness to see the practical limit per side, before the width of the collar:
| Plate | Thickness | Plates per side | Max load with 45 lb bar |
|---|---|---|---|
| Training bumper 45 lb | 3.25 in | 5 | 495 lb (225 kg) |
| Competition bumper 55 lb / 25 kg | 2.50 in | 6 | 705 lb (320 kg) |
| Cast iron 45 lb | 1.97 in | 8 | 765 lb (347 kg) |
A collar takes up another 1 to 2 in, so a sleeve that is exactly full by this count may not take a collar. Thick training bumpers run out of room fastest, which is why strong lifters who deadlift above about 500 lb switch to iron or calibrated plates. Women's bars have shorter sleeves (about 12.6 in, 320 mm), so they hold roughly a quarter fewer plates.
Why the full-size diameter matters
A 450 mm plate puts the center of the bar 225 mm (8.86 in) above the floor. Deadlift and clean technique, rack and pulling-block heights, and plate jacks are all built around that height. Two consequences:
- Mixing diameters changes the lift. A 35 lb iron plate (360 mm) sets the bar about 1.8 in (45 mm) lower than a 45 lb plate. Pulling from 35s is a deficit lift, not a standard deadlift.
- Storage needs a 450 mm space. Plate trees and wall racks for full-size plates need about 18 in (46 cm) of height or width per plate, and pegs long enough for the stack. Seven 3.25 in training bumpers need nearly 23 in (58 cm) of peg.
Planning a full set of bar, rack and bench? The power rack dimensions guide covers storage pegs and rack widths, and the home gym size guide covers floor space and flooring. For loose weights, see dumbbell sizes and kettlebell sizes.
Checking an unknown plate
- Measure the hole. About 2 in (50 mm) means Olympic; about 1 in means standard. A hole between the two is a rare regional size and should be matched to its own bar.
- Measure the diameter across the widest point. 17.7 in (450 mm) means a full-size plate or a bumper. Anything smaller is a fractional iron or steel plate.
- Weigh it if accuracy matters. Iron plates are commonly a few percent off their label. A bathroom scale is accurate enough to spot a 45 lb plate that is really 43 lb.
Frequently asked questions
Are all weight plates a standard size?
No. Only the diameter of full-size plates is close to universal: 450 mm (17.72 in) for 45 lb, 20 kg and 25 kg plates, set by the IWF and IPF competition rules. Thickness, and the diameter of every plate below 20 kg, varies by brand and material.
What size is the hole in an Olympic weight plate?
About 50 to 51 mm (1.97 to 2.01 in). Manufacturers machine the hole slightly larger than the 50 mm bar sleeve; Rogue, for example, lists 50.4 mm. Standard (non-Olympic) plates have a hole of roughly 1 to 1.2 in (27 to 31 mm) and will not fit an Olympic bar.
Do bumper plates fit a Smith machine?
Usually yes, if the Smith machine has 2 in Olympic sleeves, because bumpers use the same 50.4 mm hole. The limit is sleeve length: thick bumpers fill a short Smith sleeve quickly, so check the sleeve length against the plate thickness before buying.
Why are 10 lb bumper plates the same diameter as 45s?
So the bar sits at the same 225 mm (8.86 in) height whatever the load, which lets beginners deadlift and clean light weights from the standard floor position and lets the bar be dropped safely. To stay that wide while weighing only 10 lb, the plate is made thin, about 1 in (25 mm).
How much does a 20 kg plate weigh in pounds?
A 20 kg plate weighs 44.09 lb, about 0.9 lb less than a 45 lb plate (20.41 kg). A 25 kg plate weighs 55.12 lb. Calibrated competition plates are made to within a small fraction of a percent of their label; ordinary cast iron plates are often a few percent off.
What is the diameter of a 25 lb plate?
It depends on the type. A 25 lb bumper plate is full size, 450 mm (17.72 in). A 25 lb cast iron plate is much smaller, around 11 in (276 mm on Rogue's Deep Dish plates), and is typically 1.3 to 1.4 in thick.