Convert Miles per Gallon to Liters per Mile - Fuel Economy Converter
This converter converts fuel economy given in miles per gallon (MPG) into liters consumed per mile (L/mi). The relationship is based on the exact volumetric definition of the gallon in liters and the definition of MPG as miles traveled per one gallon of fuel.
For everyday accuracy we use the internationally accepted liter value for each gallon type (US and Imperial) and show the primary formula that professionals use when comparing fuel use across unit systems. This page provides practical guidance on which gallon definition applies, how the conversion is calculated, and typical rounding and measurement cautions.
For regulatory and engineering contexts, always specify which gallon is used (US or Imperial) and report the conversion precision. References below include U.S. government energy resources and national measurement authorities.
Governance
Record ad83bfe5cd78 • Reviewed by Fidamen Standards Committee
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Methodology
Fuel economy in MPG is miles per gallon. To get liters per mile, invert the MPG definition by expressing one gallon in liters and dividing by the MPG value.
We use the US liquid gallon value 1 US gal = 3.785411784 L for conversions unless an Imperial (UK) gallon is explicitly selected; the Imperial gallon equals 4.54609 L. The converter applies the appropriate constant and returns L/mi.
When comparing to widely published metrics (e.g., L/100 km), convert L/mi to L/100 km by multiplying L/mi by 160.9344 (100 km = 62.137119 miles). For regulatory reporting use the units and rounding required by the relevant agency.
Key takeaways
Conversion between MPG and L/mi is exact given the liter-per-gallon constant: use 3.785411784 L per US gallon or 4.54609 L per Imperial gallon and divide by MPG.
Report which gallon definition you used and include rounding or uncertainty guidance appropriate to your context (consumer display vs. regulatory reporting).
Worked examples
Example 1 (US gallon): 30 MPG → L/mi = 3.785411784 ÷ 30 = 0.12618 L/mi.
Example 2 (Imperial gallon): 30 MPG (imperial) → L/mi = 4.54609 ÷ 30 = 0.15154 L/mi.
Example 3: To express 0.12618 L/mi as L/100 km: 0.12618 × 160.9344 = 20.31 L/100 km.
F.A.Q.
Which gallon does this converter use by default?
By default the converter uses the US liquid gallon (1 US gal = 3.785411784 L). An Imperial (UK) gallon option and a note explaining the difference are provided; always confirm which gallon your MPG figure uses.
Why express fuel economy as liters per mile instead of MPG?
Liters per mile (or liters per 100 km) is a direct measure of fuel consumed per distance and is linear with fuel use—useful in engineering, fleet reporting, and emissions calculations where per-distance consumption is additive across trips. MPG is non-linear when averaged, so converting to L/mi avoids averaging bias in some analyses.
How many significant digits should I report?
For consumer-facing displays, two to three significant digits are usually sufficient (e.g., 0.126 L/mi). For regulatory or engineering work, follow the precision rules in the applicable guidance (for example, DOE/EPA and national metrology guidance) and include measurement uncertainty where required.
Does vehicle instrument error affect conversions?
Yes. Instrument-derived MPG (onboard computers, trip odometers, fuel-pump totals) include measurement error. When precision matters, estimate and report uncertainty from the measurement method; see national metrology guidance for uncertainty propagation.
How do I convert MPG (US) to liters per 100 kilometers?
First convert MPG to L/mi using L/mi = 3.785411784 ÷ MPG, then multiply L/mi by 160.9344 to get L/100 km.
Are the constants authoritative?
Yes. The liter values used for US and Imperial gallons are the internationally recognized volumetric definitions published by national measurement authorities and referenced by US government energy resources.
Sources & citations
- Fueleconomy.gov (U.S. Department of Energy and EPA) — Fuel economy basics — https://www.fueleconomy.gov
- U.S. Department of Energy — Vehicle Technologies Office (fuel economy and environment guidance) — https://www.energy.gov/eere/vehicles
- U.S. National Institute of Standards and Technology — Weights and Measures — https://www.nist.gov/pml/weights-and-measures
- U.S. Environmental Protection Agency — Green Vehicles and fuel economy — https://www.epa.gov/greenvehicles
- International Organization for Standardization (ISO) — standards and unit guidance — https://www.iso.org
- ISO 80000-3:2019 — Space and time — https://www.iso.org/standard/64974.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: ad83bfe5cd78What changed (latest)
v1.0.0 • 2025-11-26 • 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 • 2025-11-26 • 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 26, 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 • 2025-11-26 • 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: e2749fbe0361