1,645 sizes measured · strictly 18+

Girth vs diameter — what's the difference?

Girth, circumference, width around: all the same number, measured with a tape. Diameter is the distance across, and π sits between them. Type either one; we'll do the other, in every unit, at real size on your screen.

is the distance
Girth — around 5.5″ 14 cm · 140 mm
Diameter — across ~1.75″ ~4.4 cm · ~44 mm
On the shelf see everything 5–6″ around → 175 sizes in that band right now

The diameter here is derived with π, so it wears a ~ — real toys are ovals, not perfect circles. Why that matters ↓

bank card, for scale
Life-size on most laptop and desktop screens, which draw 96 pixels to the inch. Phones pack pixels differently — hold a real bank card against the dashed outline; if they match, the circle is true.

Browse by the number that matters.

Bands use the widest listed girth of each size — the number that decides fit.
under 4″ around 8 4–5″ around 67 5–6″ around 175 6–7″ around 165 7–8″ around 259 8″ and up around 971

Or start from what already fits: find my fit ranks the whole shelf against a toy you own, and the quiz gets there in six questions.

Why isn't diameter just girth ÷ π?

It almost is — that's exactly the sum we do above. But π only tells the truth about perfect circles, and toys aren't: most sculpts are gently oval, ridged, or wider one way than the other. Two toys with the same 6″ girth can have noticeably different widest-across measurements.

That's why girth (circumference) is the headline number — it's what a tape measure actually reads, whatever the cross-section shape — and why every derived diameter on this site wears a ~. Makers publish circumference for the same reason; where a diameter appears in our spec tables it's either maker-published or marked as derived.

Practical rule: compare girth to girth, and treat any diameter as a good sketch rather than a promise.

How do you measure girth?

  1. Wrap the widest point. A soft measuring tape or a piece of string, once around the thickest part — snug against the surface, not squeezing.
  2. Mark and read. Read the tape where it overlaps; with string, mark where it meets itself and lay it flat along a ruler.
  3. Measure twice, then compare. Do it again to check, then compare girth to girth — no π required.

Works the same on a toy you own and on yourself — and knowing both is the whole game. Our fit finder takes it from there.

What diameter is a 6″ girth?

Diameters are derived with π — that's what the ~ marks.
Girth (around) Same in cm ≈ Diameter (across) ≈ in mm On the shelf
4″ 10.2 cm ~1.27″ ~32 mm 4–5″ around →
4.5″ 11.4 cm ~1.43″ ~36 mm 4–5″ around →
5″ 12.7 cm ~1.59″ ~40 mm 5–6″ around →
5.5″ 14 cm ~1.75″ ~44 mm 5–6″ around →
6″ 15.2 cm ~1.91″ ~49 mm 5–6″ around →
6.5″ 16.5 cm ~2.07″ ~53 mm 6–7″ around →
7″ 17.8 cm ~2.23″ ~57 mm 7–8″ around →
7.5″ 19.1 cm ~2.39″ ~61 mm 7–8″ around →
8″ 20.3 cm ~2.55″ ~65 mm 8″ and up around →
9″ 22.9 cm ~2.86″ ~73 mm 8″ and up around →

Quick answers.

Is girth the same as circumference?
Yes. Girth is the distance all the way around the widest point — exactly what circumference means. Toy makers, tailors and tree surgeons all say girth; geometry class says circumference. Same tape measure, same number.
What diameter is a 6-inch girth?
About 1.91 inches (4.9 cm) across — if the shape were a perfect circle. 6 ÷ π ≈ 1.91. Real toys are slightly oval, so the true widest across is usually a touch more than the maths says.
How do I convert circumference to diameter?
Divide by π (3.14159). A 5.5-inch circumference is about 1.75 inches across; going the other way, multiply the diameter by π. Our converter does both, in inches, centimetres and millimetres.
Why do toy makers list circumference instead of diameter?
Because it's the repeatable measurement: you can wrap a tape around a toy, but you can't push a ruler through it. Nearly every maker we track publishes circumference; where we show a diameter we derived it with π and mark it ~.
How do I measure my own girth accurately?
Wrap a soft measuring tape (or a piece of string) around the thickest point, snug but not tight. If you used string, mark where it meets and measure the string flat against a ruler. Measure twice — it's the single number that matters most for fit.
Firmness, translated → Shore 00 numbers, maker labels and real toys, all on one ruler. The whole shelf → Every size we track, filterable by girth, length, feel and maker. Sizing up, sensibly → Know your girth and wondering what's next? The patient route up, with next-step picks from the live shelf.