Smoke Detector Placement Calculator
Work out how many smoke detectors a home needs and where they should go.
Formula and sources updated · Data sources · 2View algorithm, constants and default inputs (JSON)
About this calculator
Planning baseline only: count one alarm inside every bedroom, outside each separate sleeping area, and on every home level including the basement. Use your local fire authority and each alarm maker’s instructions to confirm the actual number and placement; local codes differ. This calculator does not estimate carbon monoxide alarms.
Worked example
calculated with the default values below
Bedrooms 3 · Above-ground home levels 2 · Separate sleeping areas outside bedrooms 1 · Basement or finished cellar Yes Baseline smoke alarm count 7
Data sources
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
D = b + h + L + k
- b
- Bedrooms
- h
- Separate sleeping areas
- L
- Above-ground home levels
- k
- Basement (0 or 1)
- D
- Planning baseline alarm count
Planning count adds bedrooms, separate sleeping-area exits, home levels and an optional basement. It is a baseline count, not a code assessment; placement depends on local rules and maker instructions.
Frequently asked questions
Is this a code-compliance count?
No. It counts a planning baseline: one alarm in each bedroom, outside each separate sleeping area, and on every home level including the basement. Local codes and each alarm maker’s instructions determine actual placement. Carbon monoxide alarms need separate guidance. See the [U.S. Fire Administration](https://www.usfa.fema.gov/prevention/home-fires/prepare-for-fire/smoke-alarms/).