How Big Is 20cm? 📏 7.87 Inches Explained

You’re looking at a product listing, a sewing pattern, or a shipping label, and the only size given is 20cm. No photo, no ruler in reach.

20cm is about 7.87 inches, or roughly 7 7/8 inches. That’s just under 8 inches and about two-thirds of a foot. It’s also about 1 cm shorter than the short side of a sheet of A4 paper.

That’s enough to check a box, a shelf, or a baking pan. Below you’ll find a conversion chart, ten everyday objects that match how long 20 cm is, and a few ways to estimate it with things already in your pocket or on your desk.

20 cm in other units

The formula is simple: inches = centimeters ÷ 2.54. That factor is exact. The inch has been defined as 2.54 cm since the international agreement of 1959, according to NIST.

Unit	20 cm equals
Inches	≈ 7.87 in (about 7 7/8 in)
Feet	≈ 0.66 ft
Yards	≈ 0.22 yd
Millimeters	200 mm
Meters	0.2 m

Is 20 cm the same as 8 inches? Almost. Eight inches is 20.32 cm, so the two differ by about 3 millimeters, roughly the thickness of two stacked coins. For shopping and packing, treat them as equal. For cutting a part that has to fit, don’t.

Ten everyday things close to 20 cm

I stopped at ten on purpose. Plenty of household objects come near 20 cm, but many vary too much from brand to brand to make a reliable reference. These ten are either labeled with an 8-inch size or built to a standard. The last column shows how far each one is from the mark.

Object	Length or width	Compared with 20 cm
Standard new pencil	About 19 cm (7.5 in)	About 1 cm short
Dinner fork	Roughly 18–21 cm	Varies by set
8-inch chef’s knife (blade only)	About 20 cm (8 in)	Very close
8-inch cake pan (diameter)	About 20 cm	Very close
8-inch flour tortilla	About 20 cm	Very close
8-inch adjustable wrench	About 20 cm	Very close
iPad mini (height, recent models)	About 19.5 cm	About 0.5 cm short
Trade paperback (height)	Roughly 20–22 cm	Often a little taller
Volleyball (diameter)	About 21 cm	About 1 cm over
A4 paper (short side)	21 cm	1 cm over

Picturing it

Twenty centimeters is a hand-and-a-half of everyday stuff. A US dollar bill is 6.14 inches (15.6 cm) long, so 20 cm is about 4 cm longer. A dinner plate is usually 25 cm or more, so 20 cm is noticeably smaller. If you’ve held a paperback, you’ve held roughly this length.

It’s also worth knowing what 20 x 20 cm looks like, since that’s a common size for baking pans, tiles, and craft squares. It’s a square just under 8 by 8 inches, close to the standard 8-inch square pan.

Ways to estimate 20 cm without a ruler

• Bank cards. A standard card is 85.6 mm long. Line up two end to end, then add about a third of another.
• Your hand. Spread your fingers and measure the span from thumb tip to little-finger tip. Check it against a ruler once. For many adults it lands between 18 and 23 cm, and after that you carry the reference with you.
• A sheet of A4. Its short side is 21 cm, so imagine shaving off a strip about as wide as a pinky nail.
• Your thumb. If your thumb is about 2.5 cm wide, eight in a row make 20 cm. Thumbs vary, so measure yours first.

Reading it on a real ruler or tape: the 20 cm mark sits about 3 mm before the 8-inch line. On an inch-only tape, look for the tick one-eighth of an inch before 8, which is 7 7/8.

The ten references, one by one

A standard pencil

A new, unsharpened pencil is about 19 cm long, so it’s slightly short. Add a centimeter, roughly the width of your little fingertip, and you’re at 20. Sharpened ones shrink fast, so use a fresh one.

A dinner fork

Most dinner forks run between about 18 and 21 cm, and sets differ. It’s handy because it’s already on the table, but if the number matters, check yours once against a ruler. Salad forks are shorter, so don’t use those.

An 8-inch chef’s knife

The 8-inch in the name refers to the blade, which is about 20 cm. The handle adds a lot more, so only count the metal. This is a good visual anchor if you cook. Use it for looking, not measuring: a knife is a poor ruler.

An 8-inch cake pan

Bakers already know this one. The pan’s inside diameter is about 20 cm, and the outer rim adds a little. If a recipe calls for a 20 cm tin, an 8-inch pan is the standard swap.

An 8-inch flour tortilla

Packaging labels these by size, so the number is printed on the bag. A tortilla is a decent way to see a 20 cm circle on a plate.

An 8-inch adjustable wrench

Wrenches are sold by length, and an 8-inch one is close to 20 cm overall. If you have a toolbox, this is the most reliable item on the list, because the size is stamped on the handle.

An iPad mini

Recent models are about 19.5 cm tall, so it’s within half a centimeter of 20. It’s a clean rectangle, which makes it useful for comparing against boxes, frames, and drawer widths.

A trade paperback

Trade paperbacks are commonly around 8 to 8.5 inches tall, roughly 20 to 22 cm. Mass-market paperbacks are shorter and hardcovers are often taller, so check the format first. Measure the height, not the width.

A volleyball

A regulation ball has a circumference of about 65 to 67 cm, which works out to a diameter near 21 cm. It’s a good mental picture for round objects such as plant pots, wheels, or bowls.

The short side of A4 paper

A4 is 21 cm by 29.7 cm under the ISO standard. Its short edge is a centimeter over our target. Because a sheet is flat, you can lay it right against whatever you’re measuring.

FAQ

How many inches is 20 cm?
About 7.87 inches, or 7 7/8 inches on a tape measure. Divide centimeters by 2.54 to convert any length.

Is 20 cm bigger than 8 inches?
No, but only barely. Eight inches is 20.32 cm, so 20 cm is about 3 mm smaller.

What household item is closest to 20 cm?
An 8-inch cake pan or an 8-inch wrench is closest. A pencil, an iPad mini, and a sheet of A4 are all within about a centimeter.

How can I measure 20 cm without a ruler?
Use two bank cards plus about a third of another, or take an A4 sheet’s short side and trim about a centimeter off it.

Final thoughts

So, how big is 20cm? About 7.87 inches, or just shy of 8, roughly the length of a new pencil plus a fingertip, or a paperback standing on its end.

For most jobs, that’s all you need. It’s close enough to size up an online listing, check if a gift will fit in a bag, or judge a gap before a small repair. Anchor it to one or two objects you know well, like a pencil or an 8-inch pan, and the number stops being abstract.

When the fit is tight, such as a cut, a frame, or a part that has to slot in, take a moment to measure with a real ruler. The 3 mm gap between 20 cm and 8 inches is small, but it’s enough to matter.