Marine & NauticalImperial Gallons to US Gallons

Imperial Gallons to US Gallons

Snapshot

1 Imperial Gallon equals 1.20095 US Gallons. Conversion Encyclopedia uses the same fixed conversion basis across the calculator, common values, and reverse page for this page.

Reference basis: This result uses fixed marine-capacity definitions for tanks, holds, and onboard volume checks.
Example: For 2 Imperial Gallons, the result equals 2.4019 US Gallons.
Use the reverse page if you need the opposite direction with the same basis.

Use the interactive calculator below for custom values and the common-value table for quick checks.

Interactive conversion

Converter Calculator

1.20095 US Gallons (US gal)

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Machine access

Available to apps and AI agents

Imperial Gallons to US Gallons can be requested through Conversion Encyclopedia's structured interfaces by software and compatible AI agents. The identifiers below select the same calculation as the calculator.

Machine-readable identifiers

Conversion family: marine
Source unit: imperial_gallons
Target unit: us_gallons

The JSON API and OpenAPI specification use the identifiers to reach the conversion engine. WebMCP lets compatible AI agents request the same calculation.

Example API request and response

POST /api/v1/convert

Request

{
  "family": "marine",
  "value": 1,
  "from": "imperial_gallons",
  "to": "us_gallons"
}

Essential response

{
  "ok": true,
  "conversion": {
    "family": "marine",
    "value": 1,
    "from": "imperial_gallons",
    "to": "us_gallons",
    "result": {
      "raw": 1.2009499255,
      "display": "1.20095"
    },
    "canonicalPath": "/marine/imperial-gallons-to-us-gallons/"
  }
}

Full API documentation

Explanation

Formula: US Gallons = Imperial Gallon × 1.20095. Why: tank and hold-capacity units are tied to fixed volume definitions, so the route normalizes through one volumetric basis before applying the target unit.

Imperial Gallons (Imp gal): a UK imperial liquid-volume unit used in some marine and fuel-capacity references.

US Gallons (US gal): a US customary liquid-volume unit used for fuel, tanks, and onboard capacity references in US-based contexts.

This route is useful when translating tank, hold, and onboard liquid-capacity values across metric and gallon-based systems for storage, fueling, and vessel operations.

This conversion is purely multiplicative because both units reduce through one fixed marine reference basis for the active family, with no offset.

Method & Marine Basis

Method basis: fixed marine-capacity definitions used for tank, hold, and fueling calculations.
Applied factor: 1 Imperial Gallon = 1.20095 US Gallons.
Consistency rule: calculator output and common-value rows use the same fixed marine constants in both directions.

Common Conversion Values

Imperial Gallon (Imp gal)	US Gallons (US gal)
1	1.20095
2	2.4019
5	6.00475
10	12.009499
20	24.018999
50	60.047496
100	120.094993

Questions & answers

Frequently Asked Questions

How many us gallons are in 1 imperial gallon?

The fixed factor gives 1 imperial gallon = 1.2009499255 us gallons.

What is the reverse conversion for Imperial Gallons to US Gallons?

Use the US Gallons to Imperial Gallons page to reverse the same tank or hold-capacity relationship for onboard volume checks.

Can I use decimal imperial gallons values?

Yes. Decimal imperial gallons values are supported for fueling, storage, and onboard capacity checks.