The short answer. In Australia a standard nip is 30 ml, and a fluid ounce is just under 30 ml, so the number on the flask is very close to the number of drinks inside it. A 3oz flask holds about three nips, a 6oz about six, an 8oz about eight. Most people are happiest with 6oz: it is the size we hold most of, 84 of our 223 flasks, and it still sits flat in a jacket. Buy 3oz or 4oz if it has to be invisible in a pocket, and 7oz or 8oz if you are passing it around.
Hip flask sizes are quoted in fluid ounces, which is not a unit most Australians use for anything else, and that is the whole reason this question gets asked. Nobody knows what 6oz means until they are holding one.
The useful coincidence is this: a US fluid ounce is 29.57 ml and an Australian standard nip is 30 ml. They are near enough the same. So the number printed on a hip flask is, for practical purposes, the number of drinks it holds. That single fact settles most of the decision, and everything below is detail on top of it.
What each size actually holds
Here is the range we stock, with what each size comes to in millilitres, roughly how many 30 ml nips that is, how many flasks we hold in that capacity, and where the prices start.
| Size | Volume | Nips (30 ml) | Flasks we hold | From |
|---|---|---|---|---|
| 3oz | about 89 ml | 3 | 10 | $35 |
| 4oz | about 118 ml | 4 | 16 | $40 |
| 5oz | about 148 ml | 5 | 21 | $35 |
| 6oz | about 177 ml | 6 | 84 | $35 |
| 7oz | about 207 ml | 7 | 10 | $50 |
| 8oz | about 237 ml | 8 | 40 | $50 |
Two honest caveats on that table. A flask filled to the absolute brim is difficult to cap without spilling, so treat the nip figures as the ceiling rather than the pour you will actually get: knock one off each and you have the comfortable number. And a few flasks in the range sit outside 3oz to 8oz entirely. We hold 1oz keyring flasks from $12, a handful of 9oz and 10oz flasks, and one or two oddities above that. They are a small part of the range and they are not what this guide is about.
3oz: the one nobody notices
A 3oz flask is a genuinely small object. Three nips, under 90 ml, and it disappears into an inside jacket pocket or a handbag without changing the line of the fabric. This is the size to buy when the flask is meant to be discreet: a wedding, a race day, a long formal evening where you want one good drink rather than a session.
We hold ten of them, starting at $35 for the Classic 3oz Stainless Steel Hip Flask, with the Matte Black 3oz at the same price if you want something less shiny. There are also round 3oz flasks with a keychain, which is about as pocketable as a flask gets, and wood-wrapped 3oz flasks at the top of that size for people who want the small format without the plain steel look.
The trade-off is obvious once you own one: three nips goes quickly, and a 3oz flask is not something you share. If two of you are drinking from it, this is the wrong size.
4oz and 5oz: the sizes in between
These two are where people land when 3oz feels mean and 6oz feels like a commitment. Four nips and five nips respectively, still slim enough for a jacket, and noticeably lighter to carry all day than the bigger flasks.
The 4oz shelf runs from $40 for the Classic 4oz Stainless Steel Hip Flask, and it is also where most of the more unusual shapes live: bracelet flasks that sit on the wrist, transparent-centre flasks, and a run of novelty designs. If you want a flask that is a talking point rather than a plain steel rectangle, look at 4oz first.
The 5oz shelf is larger, at 21 flasks, and it includes the round flasks, which are worth a mention on their own. A round flask does not curve to the body the way a classic flask does, so it is slightly less comfortable in a back pocket, but it looks quite different sitting on a table. The Round Stainless Steel 5oz Hip Flask is $55 and is the one most people mean when they ask for a round flask.
6oz: the size most people should buy
If you are buying a hip flask and you have no strong feeling about capacity, buy 6oz. Six nips is enough for an afternoon without being a bottle, and the standard 6oz curved flask is still slim enough to sit flat against a hip or in a jacket pocket. It is the size the rest of the world has settled on too, which is why 84 of our 223 flasks are 6oz and the next-largest shelf is less than half that.
It is also the size with the widest spread of finishes, from $35 at the plain end up to $180 for the heaviest luxury pieces. Some markers along that range:
- Classic 6oz Stainless Steel Hip Flask, $45. The default. Polished 6oz, nothing on it, takes engraving well.
- Wood Wrapped 6oz Hip Flask, $55. Steel body, timber wrap, warmer in the hand than bare steel.
- Luxury 6oz Hip Flask, $95. Heavier, better finished, the one to buy when it is a milestone gift.
- Military Enthusiast Pure Titanium Hip Flask, $99. The only pure titanium flask we hold. Same 6oz capacity, appreciably lighter.
That last one is worth understanding if weight matters to you. Titanium is lighter than stainless steel for the same volume, so a titanium 6oz carries more like a 4oz steel flask. You pay for it, and whether that is worth double a classic 6oz depends entirely on whether you are walking with it all day.
7oz and 8oz: the sharing sizes
Seven and eight nips is a flask for more than one person. This is the campfire, the grandstand, the boat, the third quarter at the footy. An 8oz flask is noticeably thicker than a 6oz and you will feel it in a jacket, which is the price of not running out.
We hold ten 7oz flasks from $50, including the Classic 7oz Stainless Steel Hip Flask at that price, and forty 8oz flasks from $50, starting with the Classic 8oz Stainless Steel Hip Flask. The 8oz shelf is the second-largest in the range after 6oz, and it runs up to $150 at the luxury end.
One thing to think about before you buy the biggest flask available: a full 8oz of spirit is a lot of drinks to get through in a day, and a flask that stays half-full for months is a flask you will forget to rinse. If you are buying for one person, 6oz is usually the more honest choice.
What changes with size, besides the volume
Weight. Empty, the difference between a 3oz and an 8oz is modest. Full, it is not. Spirit is roughly the weight of water, so an 8oz flask carries about 240 grams of liquid against the 3oz flask’s 90.
Pocket fit. Classic flasks are curved to sit against the body, and that curve works at every size. What changes is thickness. Above 6oz the flask starts to stand proud of a suit jacket, which matters at a wedding and does not matter at a campsite.
Engraving room. A larger face gives an engraver more to work with. A 3oz flask will take a set of initials or a short name comfortably; a longer message sits better on a 6oz or 8oz. If the wording matters more than the pocket, size up.
Price. Size is not the main driver of price on this range. Finish is. A plain 8oz at $50 costs less than a luxury 6oz at $95, and the cheapest and most expensive 6oz flasks we hold are $35 and $180. Choose the capacity first, then the finish.
Which size for which occasion
- A wedding, worn under a suit: 3oz or 4oz. Discreet beats generous here.
- A gift for someone who does not own one: 6oz. It is the safest guess in the range.
- A groomsmen or wedding party set: 6oz for a matching set, or 3oz if they will be worn all day under jackets. Our Wedding Hip Flasks category holds 48 flasks chosen for this. Check the individual product page before you plan on engraving, because not every flask in the range takes it.
- Camping, fishing, the snow: 8oz. You are sharing and you are not wearing a suit.
- A first flask, for yourself: 6oz, plain steel, around $45. If you find you never finish it, the next one is a 4oz.
- A keyring or a handbag: 1oz or 3oz. The 1oz flasks start at $12.
If you are having it engraved
On the flasks listed under Personalised Flasks, laser engraving is a $19.99 option chosen on the product page, and it adds 7 to 14 business days of processing before the flask is shipped. That is worth knowing before you buy, because it is the difference between ordering three weeks out from a wedding and ordering three days out.
Personalised flasks are blank flasks we engrave with your text. Engraved Flasks are a separate category: those arrive with a design already etched into them, there is nothing to specify, and there is no added processing time. If the date is close, that category is the faster answer.
Not every flask in the range takes engraving. The product page is the place to check, and if the engraving option is not offered there, it is not available on that flask.
Frequently asked questions
What is the most popular hip flask size?
6oz, by a wide margin. It is the size we hold most of, 84 of our 223 flasks, and it is the size most first-time buyers settle on. Six nips is enough for an afternoon and the flask still sits flat in a jacket pocket.
How many drinks does a 6oz hip flask hold?
About six, at the Australian 30 ml standard nip. A 6oz flask is roughly 177 ml. Filling it to the very brim makes it awkward to cap, so five comfortable nips is the realistic figure.
Is a 3oz hip flask too small?
Not if you want it to be invisible. Three nips is one good drink and a top-up, which is the point of a 3oz: it goes into an inside jacket pocket without showing. It is the wrong size if you plan to share it.
What size hip flask should I buy as a gift?
6oz, unless you know something specific about how they will use it. It is the most common size, the widest choice of finishes, and it suits both pocket carry and sharing. Ours start at $35 and run to $180.
Does the size change what I can put in it?
No. Neat spirits suit a flask at any size: whisky, rum, brandy, gin, vodka. What does not suit a flask, at any size, is anything with cream, sugar syrup, citrus or fizz.
The whole range, all 223 flasks, sits on All Hip Flasks, and you can narrow it by size from there.