Fidamen

Convert Kilometers per Liter to Miles per Gallon - Fuel Economy Converter

Convert kilometers per liter (km/L) to miles per gallon (MPG) quickly and accurately. This converter uses internationally recognized unit definitions so results are consistent with government and laboratory references.

Be aware there are two common MPG definitions: US (gallon = 3.785411784 L) and Imperial (gallon = 4.54609 L). By default this tool presents the widely used US gallon conversion; the methodology section shows the alternative Imperial formula and factors.

Updated Nov 12, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record a5ad5d6d3ca3 • 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

This conversion is a fixed-ratio unit conversion built from base definitions: 1 kilometer = 0.62137119223733 miles and 1 litre = 0.26417205235815 US gallons. The numeric conversion factor is therefore derived by combining those exact unit definitions.

Values and constants referenced follow NIST and federal guidance for unit definitions and fuel-economy reporting. For regulatory context on how MPG numbers are produced and rounded, see government fuel-economy resources listed in the citations.

Worked examples

Example (US MPG): 15.00 km/L × 2.352145833 ≈ 35.28 mpg (US).

Example (Imperial MPG): 15.00 km/L × 2.824809 ≈ 42.37 mpg (Imperial).

Quick check: 1.00 km/L ≈ 2.35215 mpg (US); 1.00 km/L ≈ 2.82481 mpg (Imperial).

F.A.Q.

Which MPG does this converter return by default — US or Imperial?

The default conversion shown uses the US gallon definition (1 US gallon = 3.785411784 litres). The methodology section includes the Imperial-gallon formula and factor if you need the UK/Imperial value.

Are the conversion constants exact?

The unit definitions (1 km = 0.62137119223733 miles; 1 litre = 0.26417205235815 US gallons) are the internationally accepted values used by standard bodies such as NIST. Results are mathematically exact given those definitions; displayed rounding is a presentation choice.

Why do MPG numbers from my car differ from this conversion?

Onboard trip computers and lab-rated MPG are influenced by measurement method, driving cycle, and rounding rules. Fuel economy labels (EPA, WLTP, etc.) use standardized test procedures; real-world fuel consumption also depends on temperature, driving behavior, load, and instrument calibration.

How should I measure to get an accurate km/L reading before converting?

Use a full-tank method: record odometer distance driven between fill-ups and measure fuel added (volume) at the same filling temperature/location if possible. Use calibrated pumps and account for fuel temperature if high precision is required. For regulatory-grade accuracy, follow procedures from vehicle testing authorities.

How many significant digits should I trust in the converted value?

For everyday use, two decimal places are appropriate. For engineering, lab, or regulatory use, maintain the precision consistent with your input measurement and follow the significant-figure rules from metrology guides such as NIST publications.

Do temperature and fuel density affect conversions?

This unit conversion maps volume-to-volume and length-to-length and does not account for fuel density or mass. If you need mass-based energy efficiency (e.g., MJ/kg), include fuel density and energy content in your calculation. For volume corrections by temperature, consult standards used by petroleum testing laboratories.

Where do the rounding and display rules come from?

Consumer-facing rounding typically follows regulatory or industry practice (for example, EPA label conventions). For technical reporting, use the number of digits justified by measurement uncertainty and follow guidance from metrology references.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: a5ad5d6d3ca3

What changed (latest)

v1.0.0 • 2025-11-12 • 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 12, 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 • 2025-11-12 • 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: cb54c8290584