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30 cm is 11.81 inches, or 0.98 feet (300 mm). On a US tape measure, that is just past the 11 ¾ inch mark, about 11 13⁄16 inches. It is the length of a standard school ruler, and only 4.8 mm short of a foot.
How many inches is 30 cm?
One inch is exactly 2.54 cm, so divide by 2.54: 30 ÷ 2.54 = 11.8110 inches. Rounded to two decimals, 30 cm = 11.81 in. If you need a fraction for a tape measure, the closest sixteenth is 11 13⁄16 in, and the closest eighth is 11 3⁄4 in.
| Centimeters | Inches (decimal) | Inches (nearest 1/16) | Feet |
|---|---|---|---|
| 28 cm | 11.02 | 11 | 0.92 |
| 29 cm | 11.42 | 11 7⁄16 | 0.95 |
| 29.7 cm | 11.69 | 11 11⁄16 | 0.97 |
| 30 cm | 11.81 | 11 13⁄16 | 0.98 |
| 30.48 cm | 12.00 | 12 | 1.00 |
| 31 cm | 12.20 | 12 3⁄16 | 1.02 |
| 32 cm | 12.60 | 12 5⁄8 | 1.05 |
To go the other way, multiply inches by 2.54. The cm to inches converter does both directions and works with any value.
Is 30 cm a foot?
Almost, but not quite. A foot is exactly 12 inches, which is 30.48 cm. So 30 cm is 4.8 mm (about 3/16 inch) shorter than a foot, or 98.4% of one.
For a quick estimate, “a foot is about 30 cm” works fine. The gap only matters when it adds up. Lay ten 30 cm tiles in a row and you cover 300 cm, while ten feet is 304.8 cm: the row comes up 4.8 cm (almost 2 inches) short. That is why tile layouts, shelves and cut lists should stay in one unit from start to finish.
- 30 cm in feet: 0.984 ft, which rounds to 0.98 ft.
- 30 cm in feet and inches: 0 ft 11.81 in.
- 30 cm in yards: 0.328 yd.
- 30 cm in meters: 0.3 m, and in millimeters, 300 mm.
How long is 30 cm? Things sold as 30 cm
These objects are sold under a “30 cm” size, mostly in metric countries, but you will find many of them in US stores too. Each photo is drawn to scale next to the same inch and centimeter ruler.
1. A 30 cm School Ruler
The classic answer to “what is 30 cm long?” A 30 cm ruler has a scale from 0 to 30 cm, plus a short blank margin at each end, so the plastic itself is usually about 31 cm long.
Most also carry an inch scale on the other edge, which runs to 12 inches. Because 12 inches is 30.48 cm, the 12 mark sits 4.8 mm past the 30 cm mark.
2. A 30 × 40 cm Canvas
30 × 40 cm is one of the most common canvas, poster and frame sizes in Europe. In inches, it is 11.81 × 15.75 inches, so it sits between the US 11 × 14 and 12 × 16 sizes and matches neither exactly.
If you order a frame for a 30 × 40 cm print from a US shop, look for a frame sold in centimeters, or plan on a mat: an 11 × 14 frame is too small on both sides.
3. A 30 cm Teddy Bear
Plush toys are sold by height, and 30 cm (about 12 inches) is the classic medium size: big enough to hug, small enough for a shelf or a carry-on bag.
Brands do not all measure the same way. Most give the standing height from the top of the head to the feet; some give the sitting height, so a bear sold as “30 cm sitting” is bigger overall.
4. A 30 × 30 cm Floor Tile
Tiles sold as “12 × 12” are often a little smaller than a true foot square, close to 30 × 30 cm. One 30 cm tile covers 0.09 m² (about 0.97 sq ft), so you need 11.1 tiles per square meter, before adding the usual 10% extra for cuts and breakage.
When you mix tiles from different collections, measure them: a 30 cm tile and a 30.48 cm tile will not keep the same grout lines across a room.
5. A 30 cm Cube Aquarium
Cube tanks are a favorite for small planted aquariums. A 30 cm cube is 30 × 30 × 30 cm, which holds 27 liters filled to the brim, or 7.1 US gallons.
In practice the water stays below the rim and the glass takes up some room, so the real volume is a little lower. Check the dimensions on the box: some tanks are named after their outside size, others after the glass panels.
6. A 30 cm Desk Globe
Desk globes are named by the diameter of the ball. A 30 cm globe shrinks the Earth about 42.5 million times, so 1 cm on its surface stands for about 425 km.
In the US, the classic size is the 12-inch globe, which is 30.48 cm across. Next to a 30 cm globe, you would struggle to see the difference. The base and the stand add to the height, so check the overall size if it is going on a shelf.
7. A 30 cm Zipper
Zippers are sold by length, and 30 cm is the European equivalent of the 12-inch zipper used for skirts, cushions and bags.
The length is measured from the top of the slider to the bottom stop, not along the whole tape. If your pattern calls for a 12-inch zipper, a 30 cm one is only 4.8 mm shorter and will usually do.
8. A 30 cm USB-C Cable
Short charging cables are sold as “30 cm” or “1 ft”. Both names describe the same product category: a cable long enough to link a phone to a power bank or a laptop, without a loop of slack in your bag.
Some brands measure from connector tip to connector tip, others only the cable part, so two “30 cm” cables can differ by a centimeter or two.
9. A 30 × 50 cm Lumbar Pillow
30 × 50 cm is the metric version of the US 12 × 20 inch lumbar pillow. In inches, it is 11.81 × 19.69 in, just a little smaller on both sides.
A 30 × 50 cm cover on a 12 × 20 inch insert gives a full, plump pillow; the reverse leaves the cover slightly loose.
10. 30 cm Knitting Needles
Straight knitting needles are sold by length and by diameter. 30 cm (about 12 inches) is a common length for scarves and small projects; longer needles hold more stitches.
The length does not change the size of your stitches: the diameter, in millimeters or US needle sizes, does that.
30 cm on the body
Two of the most searched “30 cm” questions are about hair and feet. Here is what 30 cm looks like in each case.
11. 30 cm of Hair
Hair grows about half an inch, roughly 1.25 cm, a month on average. At that pace, 30 cm of new hair takes about two years.
If you plan to donate a braid, check the program’s minimum. Many ask for 8 to 12 inches. 30 cm is 11.81 in, so it falls just short of a 12-inch minimum: measure in inches if that is what the program uses.
12. A 30 cm Foot
Foot length is measured from the back of the heel to the tip of the longest toe. Many brand charts put a 30 cm foot at about a US men’s 12 (UK 11, EU 46), and Japanese and Mondopoint sizes simply call it 30.
Charts differ from one brand to the next, so measure your foot and use the brand’s own table rather than converting a size.
Why are rulers 30 cm long?
It is one of the most popular “30 cm” questions on Quora. There is no single rule behind it, but a few practical reasons line up:
- It is the metric version of the foot ruler. The 12-inch ruler was the standard long before metric rulers; 30 cm is the round metric number closest to it, and many rulers carry both scales.
- It matches A4 paper. An A4 sheet is 29.7 cm long, so a 30 cm ruler can draw a line from the top to the bottom of the page.
- It fits in a school bag. Longer rulers (50 cm or 1 m) exist, but 30 cm is the longest length that still slides into most backpacks and pencil cases.
30 cm vs. 30 inches
Many searches mix up the two, and the difference is large: 30 inches is 76.2 cm, more than two and a half times longer than 30 cm. A pair of jeans with a 30-inch waist or a 30-inch inseam is measured in inches; a 30 cm measurement on clothing would be tiny.
Rule of thumb: if a number around 30 describes a body measurement on a US size chart, it is almost certainly inches. If it describes a small object sold in Europe or Asia, it is probably centimeters.
30 cm vs. 12 inches (and 30 cm vs. 40 cm)
Product names often round between the two systems: a 30 cm pan, tile or zipper is sold as “12 inch” in the US, even though 12 inches is 30.48 cm. For length, the 4.8 mm gap rarely matters.
For round things, the gap grows with the area. A 12-inch pizza has 3.2% more surface than a 30 cm pizza: you will not notice. A 40 cm pizza, on the other hand, has 78% more surface than a 30 cm one, which is why “30 cm vs 40 cm pizza” is such a common question: the bigger one is nearly twice the food.
30 × 40 cm and other sizes in inches
Frames, canvases, cushions and tiles are often listed as “30 × something” centimeters. Here are the common ones in inches.
| Size | In inches |
|---|---|
| 30 × 20 cm | 11.81 × 7.87 in |
| 30 × 30 cm | 11.81 × 11.81 in |
| 30 × 40 cm | 11.81 × 15.75 in |
| 30 × 45 cm | 11.81 × 17.72 in |
| 30 × 50 cm | 11.81 × 19.69 in |
| 30 × 60 cm | 11.81 × 23.62 in |
| 30 × 90 cm | 11.81 × 35.43 in |
- Is 30 × 40 cm A3? No. A3 paper is 29.7 × 42 cm, so an A3 print is 2 cm longer than a 30 × 40 cm frame and will need trimming.
- Is 30 × 20 cm A4? No. A4 is 21 × 29.7 cm: close, but 1 cm wider and 3 mm shorter.
30 cm vs. nearby lengths
| Length | In inches | Everyday example |
|---|---|---|
| 25 cm | 9.84 in | A dinner plate |
| 27.94 cm | 11 in | The long side of US Letter paper |
| 29.7 cm | 11.69 in | The long side of A4 paper |
| 30 cm | 11.81 in | A school ruler |
| 30.48 cm | 12 in | One foot |
| 40 cm | 15.75 in | The long side of a 30 × 40 cm canvas |
How to measure 30 cm without a ruler
- A sheet of A4 paper: the long side is 29.7 cm, only 3 mm short of 30 cm.
- A 12-inch ruler: stop just before the 12 mark; 30 cm is 3/16 inch shy of the end.
- Two US dollar bills end to end: each bill is 6.14 inches (15.6 cm) long, so two make 31.2 cm, a little over 30 cm.
- A tape measure: most US tapes have a metric scale on the lower edge; read 30 cm there rather than converting by eye.
More sizes to compare
- What 8 inches looks like: 20.32 cm, and why an “8-inch” block is 7⅝ inches
- What 9 inches looks like: 22.86 cm, from a pie dish to a paint roller
- What 10 inches looks like: 25.4 cm, from a saw blade to a 10-inch rough-in toilet
- How big 11 inches is: 27.94 cm, one inch short of a foot
- CM to inches converter: type any length in cm, with a 1–100 cm chart
FAQs
30 cm is 11.81 inches, or about 11 13⁄16 inches on a tape measure.
No. 12 inches is 30.48 cm, so 30 cm is 4.8 mm (about 3/16 inch) shorter than 12 inches.
30 cm is 0.984 feet, just under one foot.
30 × 40 cm is 11.81 × 15.75 inches.
A 30 cm pizza is 11.81 inches across, essentially a 12-inch pizza. A 40 cm pizza has about 78% more surface.
Many brand charts list a 30 cm foot as about a US men’s 12, UK 11 or EU 46. Check the brand’s own chart, as sizes vary.
Need another value? Use the cm to inches converter, or see what 11 inches looks like, a size just under 30 cm.