How to Calculate Fixture Unit (DFU)
What is Fixture Unit (DFU)?
Fixture Unit Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Total DFU = Σ Fixture Unit Values per fixture type
Step-by-Step Guide
- 1Count all plumbing fixtures, assign DFU from IPC table, sum
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
2 toilets (4ea) + 3 sinks (1ea) + 1 tub (2)
Result
Total DFU = 8 + 3 + 2 = 13 DFU
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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