Five dimensions define many round flange gaskets
Outside diameter (OD)
The finished diameter at the outer edge of the gasket.
Inside diameter (ID)
The central opening. Confirm that it clears the flow path without reducing sealing width.
Bolt-circle diameter (BCD)
The diameter of the imaginary circle through the centers of the bolt holes.
Hole count and diameter
The number of evenly spaced holes and the finished diameter of each opening.
Also record gasket thickness, material, fluid, temperature, pressure or vacuum, flange finish, bolt load, and any required standard or certification. A geometry match alone does not establish application suitability.
Measure the bolt circle without guessing
When the bolt-circle diameter is known, the designer can place evenly spaced holes and rotate the pattern by a starting angle. When only the physical flange is available, measure multiple center-to-center distances, verify the hole count, and compare the calculated pattern to the actual face.
Free bolt-circle calculator
Convert bolt-circle diameter, hole count, and starting angle into X/Y hole-center coordinates and neighboring-hole spacing.
Full-face, ring, and custom flange shapes
- Full-face: the gasket reaches the flange outside edge and includes bolt holes.
- Ring: a simple annular gasket sits inside the bolt circle and has no bolt holes.
- Non-round flange: use rectangles, rounded covers, ovals, capsules, or a line-and-curve custom outline.
- Irregular openings: add circles, rectangles, slots, or custom cutout paths inside the outside boundary.
Ordering a flange gasket online
Set the outside and band
Choose the outside shape and use a hollow version or add the measured center opening.
Add the bolt pattern
Enter bolt-circle diameter, hole count, hole diameter, and starting angle.
Price and proof
Select material, thickness, and quantity, check out securely, and approve the emailed proof.
Flange gasket pricing
Price is calculated from the chosen material and thickness, finished sheet area, total cut length, holes and other features, quantity, setup, and rush selection. A simple ring typically has fewer features than a full-face bolted gasket, but the displayed online estimate is the controlling price before shipping.