Free engineerin' tool
Bolt Circle Calculator
Punch in the bolt circle diameter and number of holes and you'll get the X/Y spot for ever' hole plus the center-to-center spacin' between neighbor holes. Measurin' a flange you don't know? Use the reverse mode to get the bolt circle from the spacin' you measured between two neighbor holes, then check it against the Texas Flange flange dimension tables.
Leave it blank = straddle the centerlines (how flanges do it)
Hole spacin'
2.8701 in
Bolt circle 7.5000 in · 8 holes ever' 45.00° · neighbor spacin' 2.8701 in · opposite holes 7.5000 in apart
| Hole | Angle | X | Y |
|---|---|---|---|
| 1 | 22.50° | 3.4645 | 1.4351 |
| 2 | 67.50° | 1.4351 | 3.4645 |
| 3 | 112.50° | -1.4351 | 3.4645 |
| 4 | 157.50° | -3.4645 | 1.4351 |
| 5 | 202.50° | -3.4645 | -1.4351 |
| 6 | 247.50° | -1.4351 | -3.4645 |
| 7 | 292.50° | 1.4351 | -3.4645 |
| 8 | 337.50° | 3.4645 | -1.4351 |
Origin's at the flange center, 0° on the +X axis, angles runnin' counterclockwise.
This here's a reference tool for plannin' and quotin'. Check it against your purchase spec and your site's procedures before y'all go usin' it.
Get y'all a flange quote
Questions Folks Ask Us
How do y'all figure the spacin' between bolt holes?
Multiply the bolt circle diameter by the sine of 180 divided by the number of holes. For an 8-hole pattern on a 7.5 inch bolt circle, dat's 7.5 × sin(22.5°) ≈ 2.870 inches.
How do I find the bolt circle diameter on a flange?
On a flange with an even hole count, measure from the center of one hole to the center of the one dead across from it. On any flange y'all can measure the spacin' between two neighbor hole centers and divide by sin(180/number of holes).
What's it mean when flange bolt holes straddle the centerline?
Standard pipe flanges lay out the holes so none of 'em sits on the up-and-down or side-to-side centerline. The first hole gets shifted over half a hole spacin', like 45° on a 4-hole flange or 22.5° on an 8-hole one.
How do I figure out what flange I got?
Measure the outside diameter, bolt circle, how many bolt holes and what size, and the thickness, then line 'em up against standard flange dimension tables, or just send 'em to Texas Flange and we'll help y'all out.
