JIS B 2401 O-Ring Size Chart (S / P / G / V)

History of JIS B 2401 Master O-Ring Size Chart Metric / ISO Chart

JIS B 2401 is the Japanese Industrial Standard for O-Ring sizes—often called “Japanese metrics.” Prints list codes such as P22, G50, or S8 instead of AS568 dashes. Dimensions are metric (ID × CS in mm).

JIS B 2401 sizes use series codes such as P22 or G50 with metric ID × CS. OD = ID + 2×CS. Code links open a product search on theoringstore.com. Interactive search: Master O-Ring Size Chart → JIS B 2401. Inch dashes: AS568 Size Chart. Metric ISO: Metric / ISO Chart.

325 JIS B 2401 sizes across S, P, G, and V series.

S series — moving / packing

Dynamic / packing applications on Japanese equipment. · 66 sizes

P series — fixed / packing

Most common fixed/packing sizes; often cited as JIS P-… on prints. · 137 sizes

G series — static

Static sealing sizes for Japanese industrial and hydraulic hardware. · 96 sizes

V series — vacuum

Vacuum-service sizes used on Japanese vacuum equipment. · 26 sizes

Source: JIS B 2401 Japanese Industrial Standard O-Ring sizes (handbook dataset). For DIN, BS 4518, SMS, NF T, and Generic Metric tooling sizes, use the Master O-Ring Size Chart.

JIS series at a glance

OD = ID + 2 × CS. A JIS size is not a drop-in for a “close” AS568 dash or ISO CS×ID without checking both dimensions and the gland.

Other size charts

Related

• Sizing overview
• Master O-Ring Size Chart
• Metric / ISO 3601 Size Chart
• AS568 O-Ring Size Chart
• How to Measure an O-Ring

History and explanation of the JIS B 2401 standard

What JIS B 2401 is

JIS B 2401 is the Japanese Industrial (now Industrial Standards / JIS) size system for O-Rings used across Japanese OEM, automotive, hydraulics, vacuum, and import equipment. Instead of an AS568 dash, sizes are identified by a series letter plus number—for example P22 or G50.

The tables on this page are the traditional S / P / G / V size families most buyers mean when they say “JIS O-Ring.”

Why Japan kept its own series codes

Like the US, Germany, and the UK, Japan standardized O-Ring sizes for domestic industry so parts would interchange. The lettered series grew around how the ring is used:

• P — packing / fixed (the series you see most on prints)
• G — static
• S — moving / packing
• V — vacuum flanges

That application-first naming is different from AS568’s cross-section-first dash groups, which is why a “close” millimeter size from ISO or a nearby AS568 dash is not automatically a JIS replacement.

How the document evolved

Shop-floor language did not change overnight. Rebuild kits and Japanese prints still say JIS P-… / G-… even when the controlling document is a newer JIS B 2401 part or an ISO-aligned callout.

JIS vs ISO vs AS568

Some modern JIS documentation also tracks ISO-style size groups. When the bag or print still uses the lettered traditional code, use this page. When it only gives mm ID × CS, start with the Metric / ISO chart.

What JIS B 2401 does not tell you

Size standards do not pick rubber. For fluid and temperature, use Materials and the Chemical Compatibility Chart. For glands, see Groove Charts.

Using this chart

1. Read the series letter and number off the print or the old ring marking/packaging.
2. Find that row in the S, P, G, or V table above.
3. Confirm ID and CS if the ring is worn or unmarked.
4. Add compound and duro, then order—or search from the code links in the tables.