ANSI Flange Dimensions and Ratings

How to measure a pump flange

ANSI flanges generally follow standard measurements. If you order just a single flange from one company, it’s measurements should very closely match that of another company. While this is true for individual flanges, it is not true for pumps. Pump casings are often designed to bolt to a ANSI flange, with similar pressure ratings of the ANSI flange. However, these flanges often do not follow all of the ANSI standard measurements.

When trying to determine the flange rating of a pump, the best method is to look for a stamp printed onto the flange. If one is not visible, or it is worn, then start by counting the number of bolt holes. This will point you to a narrower range of flange sizes in the chart below. Next measure the bolt circle diameter. In most cases, these two pieces of information is enough to determine the flange size from the charts.

If these measurements do not single out a flange, measure the bolt hole diameter. You can also double check the flange size by measuring the inner diameter of the pipe when available. The inner diameter may not be exact, but within a 1/8 inch. Not all flange sizes have a standard inner diameter and therefore are not included in the table below.

ANSI Flange Measurements and Ratings Reference Table

Bolt HolesBolt CircleBolt Hole DiameterPipe I.D.Flange SizeFlange RatingPressure Rating*
43 1/8″5/8″1.05″1″150#285 PSI
43 1/2″5/8″1.375″1 1/4″150#285 PSI
43 1/2″3/4″1.05″1″300#740 PSI
43 1/2″3/4″ 1″600#1480 PSI
43 7/8″5/8″1.61″1 1/2″150#285 PSI
43 7/8″3/4″1.38″1 1/4″300#740 PSI
43 7/8″3/4″ 1 1/4″600#1480 PSI
44″1″ 1″1500#3705 PSI
44″1″ 1″900#2220 PSI
44 3/8″1″ 1 1/4″1500#3705 PSI
44 3/8″1″ 1 1/4″900#2220 PSI
44 1/2″7/8″1.611 1/2″300#740 PSI
44 1/2″7/8″ 1 1/2″600#1480 PSI
44 1/2″1″ 1″2500#6170 PSI
44 3/4″3/4″2.07″2″150#285 PSI
44 7/8″1 1/8″ 1 1/2″1500#3705 PSI
44 7/8″1 1/8″ 1 1/2″900#2220 PSI
45 1/8″1 1/8″ 1 1/4″2500#6170 PSI
45 1/2″3/4″2.47″2 1/2″150#285 PSI
45 3/4″1 1/4″ 1 1/2″2500#6170 PSI
46″3/4″3.07″3″150#285 PSI
85″3/4″2.07″2″300#740 PSI
85″3/4″ 2″600#1480 PSI
85 7/8″7/8″2.47″2 1/2″300#740 PSI
85 7/8″7/8″ 2 1/2″600#1480 PSI
86 1/2″1″ 2″1500#3705 PSI
86 1/2″1″ 2″900#2220 PSI
86 5/8″7/8″3.07″3″300#740 PSI
86 5/8″7/8″ 3″600#1480 PSI
86 3/4″1 1/8″ 2″2500#6170 PSI
87″3/4″3.55″3 1/2″150#285 PSI
87 1/4″7/8″3.55″3 1/2″300#740 PSI
87 1/4″1″ 3 1/2″600#1480 PSI
87 1/2″3/4″4.03″4″150#285 PSI
87 1/2″1″ 3″900#2220 PSI
87 1/2″1 1/8″ 2 1/2″1500#3705 PSI
87 1/2″1 1/8″ 2 1/2″900#2220 PSI
87 3/4″1 1/4″ 2 1/2″2500#6170 PSI
87 7/8″7/8″4.03″4″300#740 PSI
88″1 1/4″ 3″1500#3705 PSI
88 1/2″7/8″5.05″5″150#285 PSI
88 1/2″1″ 4″600#1480 PSI
89″1 3/8″ 3″2500#6170 PSI
89 1/4″7/8″5.05″5″300#740 PSI
89 1/4″1 1/4″ 4″900#2220 PSI
89 1/2″7/8″6.07″6″150#285 PSI
89 1/2″1 3/8″ 4″1500#3705 PSI
810 1/2″1 1/8″ 5″600#1480 PSI
810 3/4″1 5/8″ 4″2500#6170 PSI
811″1 3/8″ 5″900#2220 PSI
811 1/2″1 1/2″ 5″1500#3705 PSI
811 3/4″7/8″7.98″8″150#285 PSI
812 3/4″1 7/8″ 5″2500#6170 PSI
814 1/2″2 1/8″ 6″2500#6170 PSI
1210 5/8″7/8″6.07″6″300#740 PSI
1211 1/2″1 1/8″ 6″600#1480 PSI
1212 1/2″1 1/4″ 6″900#2220 PSI
1212 1/2″1 1/2″ 6″1500#3705 PSI
1213″7/8″7.98″8″300#740 PSI
1213 3/4″1 1/8″ 8″600#1480 PSI
1214 1/4″1″10.02″10″150#285 PSI
1215 1/2″1 3/8″ 8″900#2220 PSI
1215 1/2″1 5/8″ 8″1500#3705 PSI
1217″7/8″12″12″150#285 PSI
1217 1/4″2″ 8″2500#6170 PSI
1219″2″ 10″1500#3705 PSI
1221 1/4″2 5/8″ 10″2500#6170 PSI
1224 3/8″2 3/4″ 12″2500#6170 PSI
1615 1/4″1 1/8″10.02″10″300#740 PSI
1617″1 3/8″ 10″600#1480 PSI
1617 3/4″1 1/8″12.00″12″300#740 PSI
1618 1/2″1 1/2″ 10″900#2220 PSI
1622 1/2″2″ 12″1500#6170 PSI
2019 1/4″1 1/4″ 12″600#1480 PSI
2021″1 3/8″ 12″900#2220 PSI

*Pump manufacturers will sometimes change the flange on a pump’s inlet or outlet. Although the pressure rating of the flange changes, the rating of the pump itself does not change. Do not attempt to pressure a pump beyond the maximum allowable pressure found on the pump nameplate or withing the user manual. Doing so may result in damage to equipment or danger to operators. 

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