Free plumbing fixture unit calculator (IPC and UPC)

2021 IPC FIXTURE UNIT CALCULATIONS

Standard:

Scope:

FIXTURE	USE	Water FU	Waste FU	TOTAL W.F.U.	TOTAL D.F.U.	Min Trap Size
Hose bibb	ALL	2.5	0.0	0.0	0.0	-
Lavatory	Private	0.7	1.0	0.0	0.0	1.25
Kitchen sink, residential	Private	1.5	2.0	0.0	0.0	1.5
Dish washer, residential	Private	1.5	2.0	0.0	0.0	1.5
2" floor drain	ALL	0.0	2.0	0.0	0.0	2
Bathroom group, flush tank	Private	3.6	5.0	0.0	0.0	-
Bathroom group, flushometer valve	Private	8.0	6.0	0.0	0.0	-
Shower head	Private	1.5	2.0	0.0	0.0	1.5
4" floor drain	ALL	0.0	8.0	0.0	0.0	sized per drain on unit
Bar sink, residential	Private	1.0	1.0	0.0	0.0	1.5
Hand sink, residential	Private	1.0	1.0	0.0	0.0	1.5
Bathtub, residential	Private	1.5	2.0	0.0	0.0	2
Automatic clothes washer, residential (8lb)	Private	1.5	2.0	0.0	0.0	2
Water closet, flushometer valve	Private	6.0	3.0	0.0	0.0	sized per drain on unit
Water closet, flush tank	Private	2.2	4.0	0.0	0.0	sized per drain on unit
Water closet, flushometer tank	ALL	2.0	0.0	0.0	0.0	-
TOTAL FIXTURE UNITS:				0	0

WASTE SIZING

—

2021 IPC Table 710.1 / UPC Table 702.1:

Total Drainage Fixture Units (DFU): 0

Drainage slope: 1/4 in/ft standard gravity building sewer.

WATER SERVICE SIZING

Total Supply Units (WSFU):0

Flush System Type:

Hunter's Peak Demand:0 GPM

Continuous / Irrigation: GPM

TOTAL DESIGN FLOW:0 GPM

Water Service Pipe

— Service

Water Meter Size

3/4" Meter

PRESSURE LOSS & RESIDUAL HEAD

Street Main Pressure: PSI

Elevation Head Loss: ft (3.9 PSI)

Meter Loss (3/4"):-0 PSI

Backflow Device Loss: PSI

Developed Pipe Run: ft (4.59 PSI)

Net Available Residual:51.51 PSI

PASS: Exceeds code minimum 15 PSI at highest fixture

Plumbing Engineering Method, IPC/UPC Tables & FAQsClick to expand ↓

Fixture Unit Method & Hunter’s Curve Calculation

Each fixture carries a water supply fixture unit (WSFU) and a drainage fixture unit (DFU) value from 2021 IPC Table 709.1/E103.3(2) or UPC Table 610.3/702.1 for private or public occupancy.

The water supply total is translated into probable simultaneous peak demand GPM using Hunter’s Curve equations. Total continuous demand (such as irrigation or cooling towers) is added directly to determine required meter and water service main sizing.

Hydraulic pressure loss calculates the net residual pressure at the highest outlet:Residual PSI = Street Static PSI − (Elevation ft × 0.433) − Meter Drop − Backflow Loss − Pipe Friction

Who uses this engineering tool

Plumbing designers & MEP drafters preparing fixture schedules and riser diagrams for permit plans
Contractors & plumbers sizing water meters and service mains for additions, ADUs, and new builds
Engineers verifying hydraulic pressure drop and PRV valve requirements (IPC 604.8)
Plan examiners confirming code compliance with 2021 IPC Table 710.1 and UPC Table 702.1

Frequently Asked Questions

What is the difference between IPC and UPC fixture values?

The International Plumbing Code (2021 IPC) and the Uniform Plumbing Code (UPC) use different fixture unit tables and Hunter’s Curve interpolations. For example, a residential flush tank toilet is 2.2 WSFU under IPC but 2.5 WSFU under UPC. This calculator supports instant switching between 2021 IPC and UPC standards while preserving your counts.

How does Hunter’s Curve calculate peak demand GPM?

Hunter’s Curve (IPC Appendix E Table E103.3(3) and UPC Table 610.3) translates non-continuous fixture unit totals into probable simultaneous peak flow in gallons per minute (GPM). Flushometer valve systems generate higher instantaneous peak demand than flush tank systems and follow a steeper curve.

How is water service pipe size determined?

Water service pipe diameter is sized based on total design flow (peak demand GPM + continuous flow like irrigation) and velocity limits (8 ft/s cold water per IPC/UPC). It is then verified against hydraulic friction loss across the developed length, meter drop, and elevation head loss.

What is the minimum required residual pressure?

Code requires at least 15 to 20 PSI residual available pressure at the highest and most remote fixture (up to 25–35 PSI for flushometer valves). If street pressure is above 80 PSI, a Pressure Reducing Valve (PRV) is mandated under IPC 604.8 and UPC 608.2.

How is building drain and sewer pipe sized?

Building drains and sewers are sized based on cumulative Drainage Fixture Units (DFU) according to IPC Table 710.1 / UPC Table 702.1 at a standard 1/4 in/ft (2%) slope. For residential dwelling units, a 4" waste pipe handles up to 216 DFUs.

Complete IPC & UPC Fixture Unit & Pipe Sizing guide →Electrical panel schedule calculator →Available fault current & AFCI/GFCI tool →Full MEP drafting permit sets →

Want the complete plumbing permit package drawn?

Send your fixture counts or floor plan sketches and get a fixed quote for complete plumbing plans, riser diagrams, and fixture schedules in AutoCAD or Revit.

Get a fixed quote