Convert Watts to BTU/h – Power Converter
This converter converts electrical or thermal power measured in watts (W) to heating/cooling rate measured in British thermal units per hour (BTU/h). The relationship is a fixed unit conversion and is appropriate when you need a direct power-rate translation (one input, one output).
Use this tool for quick sizing checks, equipment comparisons, specification reading, and documentation where a power value needs to be expressed in BTU per hour. For energy over time (for example kWh or BTU total) use an energy calculator rather than this instantaneous power-rate converter.
This page highlights the conversion factor we apply, known small variations between BTU definitions, and recommended accuracy practices including traceability to national standards and instrument calibration guidance.
Governance
Record 9cb93afd29a5 • Reviewed by Fidamen Standards Committee
Interactive Converter
Convert between watt and btu per hour with precision rounding.
Quick reference table
| Watt | BTU per Hour |
|---|---|
| 1 W | BTU 3.41 BTU/h |
| 5 W | BTU 17.06 BTU/h |
| 10 W | BTU 34.12 BTU/h |
| 25 W | BTU 85.30 BTU/h |
| 50 W | BTU 170.61 BTU/h |
| 100 W | BTU 341.21 BTU/h |
Methodology
We apply the internationally accepted conversion between SI power (watts) and BTU per hour using the joule definition of both units. The converter uses the commonly used factor where 1 watt ≈ 3.412142185 BTU/h, derived from the exact SI-Joule relationships.
Because BTU has historically had multiple closely related definitions (for example variations used in older tables or thermochemical vs international table values), small differences can appear at high precision. For regulatory, compliance, or contractual work, use the BTU definition specified in your applicable standard or test procedure.
For measurement and reporting traceability, follow calibration and uncertainty practices consistent with NIST guidance and ISO/IEC 17025 accredited laboratory procedures. For electrical power measurement best practices, consult relevant IEEE standards.
Key takeaways
This converter performs a fixed unit conversion from watts to BTU per hour using the widely adopted factor 1 W ≈ 3.412142185 BTU/h.
For routine comparisons and specifications the provided factor is appropriate. For legal, contractual, or high-precision laboratory work, confirm the required BTU definition, include uncertainty, and use traceable, calibrated instrumentation.
Worked examples
100 W → 341.2142185 BTU/h
5000 W → 17060.710925 BTU/h
0.75 W → 2.55910663875 BTU/h
F.A.Q.
Why are there slight differences in conversion factors I’ve seen elsewhere?
Small variations stem from different historical definitions of the BTU (for example international table vs older thermochemical conventions) and from rounding. For high-precision work, confirm the BTU variant required by your specification and use a factor consistent with that definition.
How many significant digits should I use?
For general use, 3–6 significant figures are typically sufficient. For laboratory or contractual measurements, follow the significant-figure and uncertainty requirements of the applicable standard or test method and include measurement uncertainty alongside any reported value.
Does this convert energy (like kWh) to BTU?
No. This converter translates instantaneous power (watts) to a rate (BTU per hour). To convert energy (for example kilowatt-hours to BTU), use an energy conversion where 1 kWh = 3412.142 BTU (approx).
How do I ensure my measurements are compliant and traceable?
Use instruments calibrated to a national standard (NIST traceability in the U.S. or an equivalent national metrology institute). Maintain calibration certificates and follow ISO/IEC 17025-accredited lab practices for test procedures and uncertainty reporting.
Are there safety or regulatory considerations when using converted values for equipment sizing?
Yes. Always verify that converted values meet the safety margins, regulatory limits, and local codes applicable to heating, ventilation, air conditioning, and electrical installations. Where required, consult a licensed engineer and applicable OSHA, local building, or electrical codes.
Sources & citations
- NIST: Guide to the SI and Units — https://physics.nist.gov/cuu/Units/units.html
- ISO/IEC 17025 — General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
- IEEE Standards and Publications — https://standards.ieee.org/
- OSHA — Occupational Safety and Health Administration — https://www.osha.gov
- ISO 80000-4:2019 — Mechanics — https://www.iso.org/standard/64975.html
- NIST SP 811 — Guide for the Use of the International System of Units — https://www.nist.gov/pml/special-publication-811
Further resources
Related tools
External guidance
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 9cb93afd29a5What changed (latest)
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 30, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 6cb9578efb42