Calculator Inputs
Example Data Table
| Scenario | Occupants | Male % | Female WCs | Male WCs | Urinals | Lavatories |
|---|---|---|---|---|---|---|
| Office planning example | 250 | 55% | 6 | 2 | 1 | 7 |
| Assembly event space | 800 | 50% | 10 | 5 | 4 | 11 |
| Industrial with showers | 180 | 70% | 3 | 2 | 1 | 4 |
Formula Used
- Male occupants = Total occupants × (Male % ÷ 100).
- Female occupants = Total occupants − Male occupants.
- Adjusted occupants = Occupants × Safety factor.
- Female WCs = ceil(Female adjusted ÷ Female ratio).
- Male fixtures = ceil(Male adjusted ÷ Male ratio).
- Urinals = floor(Male fixtures × Urinal %).
- Male WCs = max(1, Male fixtures − Urinals) if male occupants > 0.
- Lavatories = ceil(Total adjusted ÷ Lavatory ratio).
- Showers = ceil(Total adjusted ÷ Shower ratio) when enabled.
- Accessible targets = ceil(Count × Accessible %) with minimum 1.
How to Use This Calculator
- Enter the total occupant load from your egress calculations.
- Choose an occupancy type to preload typical planning ratios.
- Adjust gender split, safety factor, and any ratio fields.
- Set urinal substitution and accessibility target to match policies.
- Click Calculate to see results above the form.
- Use Download CSV or Download PDF for submittals.
- Confirm final counts with your local inspector and code official.
Technical Notes and Planning Guidance
1) Occupant load drives every fixture decision
Restroom sizing starts with the occupant load used for life-safety design. This tool assumes your occupant load is already calculated and then applies an optional safety factor to cover peak events, shift overlap, or future growth. Because fixture counts are rounded up, small changes in occupant load can create step-changes in required fixtures.
2) Gender split and ratio selection
Many projects use a planning gender split when exact staffing or audience data is unavailable. The calculator separates male and female occupant counts using your percentage, then sizes female water closets from a female ratio and male fixtures from a male ratio. Ratios are editable so you can match your adopted plumbing code or owner standards.
3) Urinal substitution and minimum male water closets
Urinals can reduce queue time and piping runs, but substitution is commonly limited. Here, the urinal percentage sets the maximum portion of male fixtures that may be urinals. The calculator also enforces at least one male water closet whenever the male occupant count is above zero, supporting basic functionality and operational resilience.
4) Lavatories, service sinks, and showers
Lavatories are sized from the total adjusted occupant load because handwashing demand is shared across users. Service sinks are treated as a minimum planning quantity for cleaning operations. Optional showers support industrial, fitness, or high-dust environments; when enabled, showers are calculated from a user-defined occupants-per-shower ratio for quick scoping.
5) Accessibility targets and documentation outputs
Accessibility needs depend on local requirements and the fixture layout. This calculator provides a target count for accessible water closets and lavatories using your percentage setting and a minimum of one when fixtures exist. Export to CSV for quantity takeoffs or to PDF for coordination notes, then confirm final compliance during permit review.
FAQs
1) Are these counts compliant with every plumbing code?
No. Codes vary by jurisdiction and occupancy classification. Use the ratio fields to match your adopted code and confirm with the authority having jurisdiction before finalizing drawings.
2) Why does the calculator round up?
Fixture requirements are typically whole numbers. Rounding up (ceiling) provides a conservative plan and prevents under-sizing when occupant loads fall between ratio breakpoints.
3) What does the safety factor change?
It increases the occupant load used for sizing, which can add fixtures when a project is near a ratio threshold. It is a planning buffer, not a replacement for code requirements.
4) How are urinals calculated?
Male fixtures are sized from the male ratio, then the urinal substitution percentage limits how many of those fixtures may be urinals. The remaining fixtures are counted as male water closets.
5) Why is at least one male water closet enforced?
Even when urinals are allowed, a water closet is typically needed for accessibility, operational needs, and user preference. The tool keeps one WC whenever male occupants are greater than zero.
6) Should lavatories be split by gender too?
Some standards split lavatories by room, while others allow shared counts. This calculator sizes lavatories from total occupants to support shared demand; adjust the ratio or counts to match your design approach.
7) How should I use the CSV and PDF exports?
Use CSV for estimating, schedules, and quantity checks. Use the PDF for coordination notes and permit discussions. Always attach the assumptions and the ratio source used for traceability.