Fidamen

Convert Miles per Gallon UK to Liters per Mile - Fuel Economy Converter

This converter turns a fuel economy value expressed in miles per imperial gallon (MPG, UK/imperial) into liters consumed per mile (L/mi). The conversion uses the exact imperial gallon definition to produce a deterministic numeric result suitable for engineering, reporting, or comparison.

Use the tool to compare vehicles, translate manufacturer figures, or prepare data for further calculations (for example converting to L/100 km). Review the methodology and FAQs for information on precision, differences between US and Imperial gallons, and measurement limits.

Updated Nov 18, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record df065d0314fd • Reviewed by Fidamen Standards Committee

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Methodology

The imperial gallon is defined as exactly 4.54609 liters. Miles per gallon (MPG) expresses distance traveled per unit of fuel volume; liters per mile (L/mi) expresses volume consumed per unit distance. Convert by dividing the liter volume of one imperial gallon by the MPG value.

This is a fixed mathematical relationship (no empirical coefficients). For traceable reporting and auditing, apply NIST/ISO measurement best practices: use NIST-traceable flow meters or calibrated fuel measurement methods and report the number of significant figures reflecting instrument uncertainty.

Accuracy caveat: this conversion provides exact arithmetic based on unit definitions. Real-world fuel consumption varies with driving conditions, measurement method, temperature, and fuel density. For regulatory or safety-critical uses, follow applicable standards for measurement equipment calibration and uncertainty reporting (see citations).

Worked examples

Example 1: 50 MPG (UK) → L/mi = 4.54609 / 50 = 0.0909218 L/mi (rounded 0.09092 L/mi).

Example 2: 30 MPG (UK) → L/mi = 4.54609 / 30 = 0.1515363 L/mi (rounded 0.15154 L/mi).

Example 3: 40 MPG (UK) → L/mi = 4.54609 / 40 = 0.11365225 L/mi (rounded 0.11365 L/mi).

F.A.Q.

What is the difference between UK (imperial) MPG and US MPG?

Imperial (UK) and US gallons are different sizes. One imperial gallon = 4.54609 liters; one US gallon = 3.785411784 liters. This converter uses the imperial gallon. Converting US MPG requires using the US gallon volume instead of 4.54609 L.

How many significant figures should I report?

Report as many significant figures as justified by measurement uncertainty. For routine comparisons, two to three significant digits are common. For instrument-calibrated measurements used in compliance, follow the uncertainty statement from your calibration certificate and relevant ISO/NIST guidance.

Is this conversion valid for regulatory reporting or vehicle lab tests?

The numeric conversion is exact for unit translation. For regulatory or lab reporting, ensure fuel volume and distance measurements are performed and documented in accordance with applicable standards and local regulations; report measurement uncertainty and traceability to NIST/ISO where required.

Why might the converted value differ from manufacturer specifications?

Manufacturer figures are often averaged from test cycles under controlled conditions and may use different rounding rules or reporting units (for example L/100 km). Real-world driving, measurement method differences, fuel quality and temperature all affect observed consumption.

How do I convert the result to L/100 km?

First compute L/mi as 4.54609 / MPG(UK). Then multiply that L/mi value by 62.137119 to get L/100 km. This multiplier is exact given mile-to-kilometer conversion 1 mi = 1.609344 km.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: df065d0314fd

What changed (latest)

v1.0.0 • 2025-11-18 • 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 18, 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 • 2025-11-18 • 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: 724f536e9e63