Fidamen

Convert Joules to Therms - Energy Converter

This converter translates energy values given in joules (J) into therms using the commonly applied US therm definition (1 therm = 100,000 BTU). Use it for engineering estimates, utility comparisons, and reporting where therms are the required unit.

Values are calculated from standard definitions: the joule is the SI unit of energy and the therm is defined in practice via the British thermal unit (BTU). For regulatory or billing use, confirm whether your context uses the US therm or a regional variant.

Updated Nov 19, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 88bae25ed499 • Reviewed by Fidamen Standards Committee

Interactive converter unavailable for this calculator.

We could not resolve compatible units for this experience. Please verify the slug follows the pattern `from-unit-to-unit-converter`.

Methodology

We use established physical constants: 1 BTU = 1,055.05585262 J (NIST reference values). The US therm is defined as 100,000 BTU, so 1 therm = 100,000 × 1,055.05585262 J = 105,505,585.262 J.

Conversion is implemented as a direct fixed-ratio transformation (no iterative methods). For display we round results by default to a sensible number of significant digits but provide exact-step formulas so you can reproduce results to any required precision.

Worked examples

Example 1: 1,000,000 J → 1,000,000 ÷ 105,505,585.262 ≈ 0.00947817 therm

Example 2: 100,000,000 J → 100,000,000 ÷ 105,505,585.262 ≈ 0.947817 therm

Single-joule conversion: 1 J ≈ 9.478171 × 10^-9 therm

F.A.Q.

Which definition of therm does this converter use?

This tool uses the US therm definition (1 therm = 100,000 BTU). If you require a different regional definition, verify with your regulator or utility and use the appropriate multiplier.

What constants and references back these numbers?

The conversion uses the NIST-referenced value for the BTU in joules (1 BTU = 1,055.05585262 J) and the common US therm definition of 100,000 BTU. See NIST and U.S. energy agency references in the citations for authoritative details.

How much precision should I display for reports or billing?

For billing or regulatory reports, follow the precision requirements of the target agency or utility (often 3–6 significant digits). For scientific calculations keep track of measurement uncertainty and round only in final reporting.

Are there other therm variants I should be aware of?

Yes. Different jurisdictions or historical sources may use alternative definitions (for example, therm of 100 kBtu vs metric-adapted variants). Always confirm the required definition with the recipient of your data.

Can I trust direct conversions for energy-efficiency compliance?

Direct unit conversions are mathematically reliable, but compliance also depends on measurement method, instrument calibration, and whether the regulator accepts the unit definition. Keep calibration certificates and reference the authoritative constants when submitting results.

How does instrument uncertainty affect converted values?

Instrument uncertainty propagates through the conversion linearly. If your energy meter has ±1% uncertainty, converted therm values carry the same relative uncertainty. Document uncertainty and include it in final reporting where required.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 88bae25ed499

What changed (latest)

v1.0.0 • 2025-11-19 • 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 19, 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 • 2025-11-19 • 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: f60d6ce82b43