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Ounces to Gallons Calculator

Convert ounces to gallons (and gallons back to ounces) for liquids and cooking ingredients. Switch between fluid ounces (volume) and weight ounces (mass), pick US or UK gallons, and choose an ingredient — the converter handles the density math for you.

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Created by

Daniel Whitman

Reviewed by

Portrait of Hannah Brooks, calculator reviewerHannah Brooks

Ounces to gallons converter

Result
1
US gallon
Input
128 US fl oz
In millilitres
3,785.41 mL
In litres
3.785 L

Quick rules: 128 US fl oz = 1 US gallon · 160 UK fl oz = 1 UK gallon · oz (weight) = gal × 133.5265 × density (g/mL).

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How this oz to gallons converter works

For fluid ounces the conversion is purely volume. The calculator multiplies your fluid ounces by the volume of one fluid ounce in millilitres (≈ 29.5735 mL for US fl oz, ≈ 28.4131 mL for UK fl oz) and divides by the volume of one gallon in your chosen gallon definition. With US fl oz and US gallons, the rule collapses to: 128 fluid ounces = 1 gallon.

For weight ounces the conversion needs density. The formula is gallons = ounces ÷ (133.5265 × density g/mL), where 133.5265 is the volume of one US gallon (3785.41 mL) divided by one ounce (28.3495 g). Pick the ingredient (or enter a custom density) and the calculator does the math for both directions.

Gallon & ounce conversion tables

Quick-glance charts for the most common conversions plus the official volume of every gallon definition used here.

US fl oz → US gallons

Chart
Fluid ouncesGallonsLitres
8 fl oz0.06250.2366
16 fl oz0.1250.4732
32 fl oz0.250.9464
64 fl oz0.51.893
96 fl oz0.752.839
128 fl oz13.785
160 fl oz1.254.732
192 fl oz1.55.678
256 fl oz27.571
384 fl oz311.356
512 fl oz415.142

US gallons → US fl oz

Chart
GallonsFluid ouncesLitres
0.125160.4732
0.25320.9464
0.5641.893
0.75962.839
11283.785
1.51925.678
22567.571
338411.356
564018.927
101,28037.854

Weight oz → US gallons (by ingredient)

Cooking
WeightWaterMilkCooking oilAll-purpose flourGranulated sugar
1 oz0.007 gal0.007 gal0.009 gal0.014 gal0.009 gal
2 oz0.015 gal0.015 gal0.017 gal0.028 gal0.018 gal
4 oz0.030 gal0.029 gal0.034 gal0.057 gal0.035 gal
8 oz0.060 gal0.058 gal0.068 gal0.113 gal0.071 gal
12 oz0.090 gal0.087 gal0.102 gal0.170 gal0.106 gal
16 oz0.120 gal0.116 gal0.136 gal0.227 gal0.142 gal
20 oz0.150 gal0.145 gal0.170 gal0.283 gal0.177 gal

Gallon definitions used here

Reference
Gallon typeVolume (mL)Notes
US gallon3,785.41128 US fl oz; 4 US quarts
UK imperial gallon4,546.09160 UK fl oz; British fuel & recipes

Frequently asked questions

How many ounces are in a gallon?
1 US gallon = 128 US fl oz; 1 UK gallon = 160 UK fl oz. For weight ounces, multiply the volume by the ingredient density — water is ≈ 133.53 oz/gal, flour ≈ 70.6 oz/gal.
What is the difference between fluid ounces and weight ounces?
A fluid ounce measures volume; a weight ounce measures mass. They are only equal for water — for everything else, density matters.
How do I convert weight ounces to gallons using density?
gallons = ounces ÷ (133.5265 × density g/mL). The 133.5265 factor is one US gallon (3785.41 mL) divided by one ounce (28.3495 g).
Is a UK gallon bigger than a US gallon?
Yes — a UK gallon (≈ 4546.09 mL) is about 20% larger than a US gallon (≈ 3785.41 mL).
How accurate are the ingredient densities?
Built-in densities are typical room-temperature values from standard references — accurate for everyday recipes, but compaction, brand and temperature can shift values a few percent.
Is this calculator free?
Yes — free and runs entirely in your browser, with no account. Contact the team if you have feedback.

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