How Many Cups In a Gallon?

Question asked by Jeff:

I agreed to try the Water Gallon Challenge (drinking a gallon of water a day for a month). I think I'll invest in a gallon water jug if I decide to do this longer than a day. But, in the meantime, to get me started, can you tell me how many cups there are in a gallon?

Follow-up responses...

Converting From Gallons To Cups

posted by Alastair:

Hi Jeff. Wow, a gallon is a lot of water to drink in a day - just how much will become evident in this article. Before I start, I do need to say that I will be looking at this purely to answer your question of how many cups there are in a gallon. I'm not going to cover the angle of whether it's healthy or not (I'm not medically qualified for that).

When looking at converting gallons to cups, your geographic location becomes important. Why? Well, there are multiple measurements for both the gallon and the cup. You haven't said where you are based, so I will cover all countries.

The gallon is a unit of measurement for liquid volume. A US liquid gallon measures 3.785 liters (rounded), where-as the imperial (UK) gallon measures 4.546 litres (rounded). That's a significant difference - the imperial gallon is 20% larger than the US gallon. It must therefore become an important consideration for the Water Gallon Challenge - you could be drinking an extra 20% if you use UK measurements.

Gallon measurements

  • US liquid gallon: 3.785411784 L
  • US dry gallon: 4.405 L (rarely used)
  • Imperial (UK) gallon: 4.54609 L

Cup measurements

When it comes to the cup, there are again different sizes. The three main ones to be aware of are:

  1. US cup: 236.588 mL
  2. Imperial cup (pre-1970s UK recipes): 284.131 mL
  3. Metric cup (used in UK and Commonwealth countries): 250 mL

That's the background information done. Let's move on to the actual conversions...

US gallon to cups

  • 1 Gallon (US, fluid) = 16 Cups (US)
  • 1 Gallon (Dry, US) = 18.618355 Cups (US)

UK gallon to cups

  • 1 Gallon (UK, imperial) = 16 Cups (UK, imperial)
  • 1 Gallon (UK, imperial) = 18.18436 Cups (metric)

Bearing in mind the 20% difference between the US gallon and imperial gallon, if you're in the UK and looking to do the 'Water Gallon Challenge' you may want to consider the conversion for US gallons to metric cups. 1 Gallon (US, fluid) = 15.1416 metric cups.

Gallons to cups conversion table

Featured below is a reference table of conversions to help you see how many cups there are in a gallon. This chart assumes you're either using the US fluid gallon and cup or the UK gallon and imperial cup.

For assistance with converting between other variants of the gallon and cup, or to convert a specific number of gallons not shown in this chart, please give the liquid volume converter a try.

Gallon (liquid) Cups Gallon (liquid) Cups
1 16 21 336
2 32 22 352
3 48 23 368
4 64 24 384
5 80 25 400
6 96 26 416
7 112 27 432
8 128 28 448
9 144 29 464
10 160 30 480
11 176 31 496
12 192 32 512
13 208 33 528
14 224 34 544
15 240 35 560
16 256 36 576
17 272 37 592
18 288 38 608
19 304 39 624
20 320 40 640

If you have any questions or comments, please leave them below.

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