Calculate drainage fixture units for plumbing drain and waste systems. Estimate total DFU, adjusted DFU load, fixture count totals, approximate drain demand, and suggested drain pipe size for sinks, toilets, showers, tubs, laundry drains, floor drains, bathroom groups, and commercial fixture groups.
Single fixture type:
The calculator multiplies the number of fixtures by the selected DFU value.
Fixture group:
The calculator multiplies the number of fixture groups by the DFU value per group.
Custom DFU:
The calculator uses your entered DFU total and applies simultaneous use and safety factor adjustments.
Drain size estimate:
The calculator uses the adjusted DFU load to suggest a rough drain pipe size for early planning.
A DFU calculator helps estimate drainage load before sizing branch drains, stacks, fixture drains, and building drains.
It can help compare fixture count, DFU value, total DFU, adjusted DFU, pipe slope, estimated pipe capacity, and suggested drain pipe size.
Your result shows an estimated drainage fixture unit load and rough drain size guidance. DFU values and pipe sizing are code-sensitive. Use this calculator as an early planning tool only. Final design should follow local plumbing code and be verified by a qualified plumber or designer.
DFU means drainage fixture unit. It is a plumbing design value used to estimate the drainage load from plumbing fixtures.
Multiply the number of fixtures by the DFU value for each fixture type, then add the totals together. Local code tables should be used for final values.
No. DFU is used for drainage, waste, and vent sizing. Water supply fixture units are used for water supply demand and pipe sizing.
No. This calculator gives a planning estimate. Final DFU calculations and pipe sizes should follow local plumbing code.