WATER METER SIZE
Water meter and service pipe size chart — IPC Table E104.1
Maximum water supply fixture units (WSFU) allowed on each meter and pipe combination in the 40–49 psi pressure band. Read across to the developed length of your run — meter to the most remote fixture, plus about 20% for fittings. The meter and the pipe are sized together; a bigger meter on undersized pipe buys nothing.
| Meter | Pipe | 40 ft | 60 ft | 100 ft | 150 ft | 200 ft | 300 ft |
|---|---|---|---|---|---|---|---|
| ¾" | ½" | 3 | 2.5 | 1.5 | 1.5 | 1 | 0.5 |
| ¾" | ¾" | 9.5 | 9.5 | 7 | 5.5 | 4.5 | 3 |
| ¾" | 1" | 32 | 32 | 26 | 18 | 13.5 | 9 |
| 1" | 1" | 32 | 32 | 32 | 21 | 15 | 9.5 |
| ¾" | 1¼" | 32 | 32 | 32 | 32 | 32 | 27 |
| 1" | 1¼" | 80 | 80 | 80 | 65 | 52 | 35 |
| 1½" | 1¼" | 80 | 80 | 80 | 75 | 59 | 39 |
| 1" | 1½" | 87 | 87 | 87 | 87 | 87 | 78 |
| 1½" | 1½" | 151 | 151 | 151 | 151 | 130 | 93 |
| 2" | 1½" | 151 | 151 | 151 | 151 | 139 | 98 |
| 1" | 2" | 87 | 87 | 87 | 87 | 87 | 87 |
| 1½" | 2" | 275 | 275 | 275 | 275 | 275 | 238 |
| 2" | 2" | 365 | 365 | 365 | 365 | 349 | 270 |
| 2" | 2½" | 533 | 533 | 533 | 533 | 533 | 528 |
IPC 2021 Table E104.1, 40–49 psi band, values read from the code text.
The code carries four pressure bands and ten lengths — this is one slice. Run your own pressure and length above.
About this calculator
This water meter size calculator returns the minimum meter and service size permitted by the 2021 International Plumbing Code, Table E104.1, along with the distribution pipe size that goes with it. Meter sizing is not a single number: the same fixture-unit load needs a bigger meter and pipe as the run gets longer and as street pressure drops. A ¾" meter and service carries 32 WSFU on a short run at low pressure but only about 4.5 WSFU at 500 feet — a seven-fold spread that a flow-rating-only calculator cannot express. The result also reports the AWWA displacement-meter flow ratings as a cross-check. ESTIMATE ONLY — verify with a licensed plumber and your local plumbing code before installation.
How to use this calculator
Enter three things.
1. Total Water Supply Fixture Units for the building — sum the fixture load values from IPC Table E103.3(2), or use the water supply pipe sizing calculator.
2. Minimum daily static pressure available at the main. Your water utility publishes this; IPC Appendix E sorts it into four bands (30-39, 40-49, 50-60, and over 60 psi).
3. Maximum developed length — the actual pipe run from the meter to the most remote fixture outlet, plus the equivalent length of fittings. IPC E103.3 suggests multiplying the measured run by about 1.2 to account for fittings.
The calculator reads down the developed-length column for your pressure band and returns the first row that carries your fixture load, exactly as IPC Appendix E Step 4 describes. Your local water utility owns the meter and has final say on the connection size.
Worked example
Typical single-family 2-bath house: about 20 WSFU, 50-60 psi at the main, 100 ft developed length.
Read down the 100 ft column in the 50-60 psi band. The ¾" meter with ¾" distribution pipe carries only 8.5 WSFU — not enough. The next row, ¾" meter with 1" distribution pipe, carries 32 WSFU. Result: ¾" meter and service, 1" distribution pipe.
This is why a 1" meter is rare on a house. A ¾" meter and service tops out at 32 WSFU in Table E104.1, and a typical house never reaches it. The utility then sets a ⅝" × ¾" meter on that ¾" service, which is the meter on roughly four out of five US homes.
Same house, long rural run: 20 WSFU, 30-39 psi, 400 ft. The ¾"/1" row now carries only 5.5 WSFU and the ¾"/1¼" row carries 13. You need the 1" meter with 1½" distribution pipe row (45 WSFU) to cover 20. Identical house, bigger meter — because of distance and pressure, not fixtures.
Small apartment building: 87 WSFU, 50-60 psi, 150 ft. A 1" meter with 1½" pipe carries 87 exactly. Note the code caps a 1" meter at 87 WSFU no matter how large the distribution pipe gets.
Common mistakes & waste factors
Sizing on fixture count alone. Developed length and available pressure move the answer more than fixture units do. The same ¾" meter and 1" pipe carries 32 WSFU at 40 ft and 4.5 WSFU at 500 ft in the 30-39 psi band.
Ignoring the distribution pipe. Table E104.1 sizes the meter and the pipe together. Putting a bigger meter on undersized distribution pipe buys almost nothing — the ¾" meter row jumps from 9.5 to 32 WSFU purely by going from ¾" to 1" pipe.
Assuming a bigger meter always helps. The code caps a 1" meter at 87 WSFU even on 2" pipe. Past that the meter itself is the limit.
Forgetting irrigation. A 4-zone system pulling 8 GPM per zone is not in the WSFU table but absolutely consumes meter capacity. Check it against the AWWA flow rating separately.
Under-registering at low flows. A meter oversized for the demand fails to register slow leaks such as a toilet flapper drip.
Rules of thumb
IPC Table E104.1 lists no meter smaller than ¾", because IPC Section 604 sets a ¾" minimum water service. The ⅝" × ¾" meter utilities install sits on that ¾" service.
A ¾" meter and service carries at most 32 WSFU — enough for nearly any single-family house on a normal run.
A 1" meter carries at most 87 WSFU regardless of distribution pipe size.
Distribution pipe size often matters more than meter size: going from ¾" to 1" pipe on a ¾" meter takes you from 9.5 to 32 WSFU.
AWWA displacement flow ratings, for cross-checking irrigation and tankless loads: ⅝" × ¾" = 10 GPM continuous / 20 GPM intermittent, ¾" = 15/30, 1" = 25/50, 1½" = 50/100, 2" = 80/160.
Utility tap fees scale with meter size — often $500-$3,000 between ¾" and 1".