How to Measure Ring Size (Japanese "Go") | Checking at Home | Column

In Japan, ring size is expressed in "go." Here we introduce the steps to roughly measure your size at home and points for getting an accurate fit. A final size check in store is recommended, but knowing a rough figure makes choosing easier.

What to prepare

A thin paper strip (or thread), a pen, and a ruler. A ring sizer would be ideal.

Step 1 | Wrap the paper strip around your finger

Wrap the paper strip once around the base of the finger you want to measure — not too tight, not too loose.

Step 2 | Mark it and measure the length

Mark where the strip overlaps, take it off, and measure the length (mm = the circumference of the finger) with a ruler.

Step 3 | Find the go guideline from the circumference

The circumference (mm) gives a guideline for the go (e.g., about 47mm → about go 7, about 49mm → about go 9, about 51mm → about go 11). If your knuckle is thick, also check a size that passes over the knuckle.

Step 4 | Re-check at different times of day

Fingers change size with morning/evening and swelling. Measuring at several times is more accurate. It also changes between summer and winter.

Points to note when measuring

Don't wrap too tightly (it reads smaller than the true size).
The go can differ between your dominant and non-dominant hand.
Since a wedding ring is worn daily, also allow room to slide it on and off.

Finding your partner's size for a surprise

Guideline of go and inner circumference

Inner circumference guideline	Japanese go
About 47mm	About go 7
About 49mm	About go 9
About 51mm	About go 11
About 54mm	About go 14

Factors that change the size

Swelling: changes with morning and night, and your condition.
Season: tends to be larger in summer, smaller in winter.
Knuckle thickness: also check a size that passes over the knuckle.

Points to note when measuring

Don't wrap too tightly (it reads smaller than the true size)
The size can differ on the non-dominant hand
Since a wedding ring is worn daily, allow room to slide it on and off

About resizing

It is reassuring to confirm in advance whether resizing after purchase is available, and the free scope, number of times, and period. Depending on the design, the range that can be resized may be limited.

A tool for accurate measuring (ring gauge)

Home measuring is only a guide. Stores have a ring gauge (sizing sticks / sizing rings) to slide onto your finger and confirm the go. The final size is most reliably measured at the store where you buy.

Size tendencies for men and women

Individual variation is large, but as a general guideline, women are often around go 7–13 and men around go 13–21. Those with thicker knuckles should not forget to check a size that passes over the knuckle.

Common mistakes in choosing a size

Measured at a swollen time of day, then it became loose later
Chose a tight fit, making it hard to slide on and off
Didn't base it on the knuckle, so it spins after wearing

When unsure, a slightly roomier size, plus confirming whether resizing is available, is reassuring.

You can gently borrow a ring they usually wear and measure its inner diameter, or ask family to help. If that's difficult, confirming with the store whether resizing after purchase is available is reassuring. For checking the real thing and measuring, head to a nearby store from Store Search.

FAQ

What determines ring size?

It's determined by the circumference of your finger (mm), expressed in Japan as a "go" (size number). A circumference of about 47mm corresponds to roughly size 7, and about 51mm to roughly size 11, as a general guide.

How can I find out my partner's ring size for a surprise proposal?

The most reliable methods are measuring the inner diameter of a ring they already wear, or asking a family member for help. If this is difficult, it's reassuring to check with the store beforehand whether resizing is available after purchase.

Is there a best time of day to measure?

Since fingers change size due to swelling, it's recommended to measure at several different times, such as morning and night. There can also be differences between summer and winter.

Does ring size change between summer and winter?

Yes. Fingers tend to be larger in summer and smaller in winter, and size can also vary with swelling or physical condition. We recommend measuring at several different times.

Can the ring size be adjusted later?

Many stores offer resizing, but the free range, number of times allowed, and the extent of adjustment possible vary by design and store. Be sure to check before purchasing.

Can my size be measured accurately in-store?

Yes. You can try on an actual ring gauge (sizing stick) at the store to check your size. Measuring at home is just a rough guide, so we recommend getting measured in-store for the final confirmation.

Which is better, a snug fit or a looser fit?

A little room to slide the ring on and off comfortably is reassuring. Since finger size can change with swelling, it's best to measure at different times of day before deciding.