You're standing in the kitchen, staring at a jigger or a measuring cup, and the recipe just says "1.5 oz." It sounds simple. It's just a shot, right? Well, sort of. If you're looking for the quick answer, 1.5 oz is 44.36 milliliters.
Most people just round that up to 45 ml. It’s easier. It fits the lines on those little stainless steel cups better. But if you’re doing laboratory work or high-stakes baking, that tiny decimal matters. Precision is a fickle friend.
The math behind 1.5 oz is how many ml
We have to talk about the conversion factor. One fluid ounce in the US system is technically 29.5735 ml. When you multiply that by 1.5, you get the 44.36 figure.
However, the world isn't unified on what an "ounce" actually is. It's a mess. In the UK, they use the Imperial fluid ounce. That’s about 28.41 ml. If you’re following a British cocktail book and you use the US conversion, your drink is going to be slightly too strong. Not the worst problem to have on a Friday night, but it’ll throw off the balance of a delicate drink like a Paper Plane or a Last Word.
Then there’s the "label ounce." The FDA, in its infinite wisdom, decided that for food labeling, one fluid ounce is exactly 30 ml. This makes the math cleaner for nutrition facts. If you see a bottle of soda that says it contains 1.5 oz of a certain ingredient, they probably mean 45 ml.
👉 See also: Custard for Tarts Recipe: Why Your Pastry Cream Is Breaking and How to Fix It
So, why does this matter?
Because "close enough" works for a stew, but it fails for a souffle.
The "Shot Glass" Confusion
In the United States, the standard "jigger" or shot size is 1.5 ounces. This is the baseline for almost every nutritional calculation regarding alcohol consumption. When the CDC or other health organizations talk about a "standard drink," they are referring to that 44 ml mark for 80-proof spirits.
But go to a bar and look at the glassware. Some shot glasses are "pony shots" at 1 ounce. Others are "double shots" at 2 ounces or more. If you're trying to track your intake or follow a specific drink recipe, you can't just assume the glass is 1.5 oz.
I’ve seen home bartenders get frustrated because their Margaritas taste like battery acid. Usually, it's because they used a 2-ounce glass thinking it was 1.5. That extra 15 ml of tequila completely overpowers the lime and agave. It’s a small volume, but a huge percentage increase.
Baking vs. Mixology: Where the 1.5 oz matters most
Baking is chemistry. If you're adding 1.5 oz of vanilla extract or almond milk to a recipe, you’re adding volume that affects the hydration of your flour.
1.5 US fluid ounces = 44.36 ml
1.5 UK fluid ounces = 42.61 ml
It’s a tiny difference, but in a recipe that requires four or five different liquid measurements, those discrepancies add up. Professional pastry chefs like Claire Saffitz or Stella Parks often argue for weighing everything in grams instead of using volume. Water (and many thin liquids) has a 1:1 ratio—1 ml is 1 gram. So, if you need 1.5 oz, you’re looking for roughly 44 grams on a digital scale.
It's just more reliable.
🔗 Read more: Black Bull Extreme Don't Quit: What Most People Get Wrong
Understanding the "Fluid" vs "Dry" Ounce Trap
This is where most people lose their minds.
An ounce can be a measure of weight (mass) or a measure of volume (fluid). When we ask 1.5 oz is how many ml, we are strictly talking about fluid ounces.
If you put 1.5 ounces of feathers on a scale, it’ll weigh 42.5 grams. If you put 1.5 ounces of lead, it’s still 42.5 grams. But if you try to measure the volume of 1.5 ounces of honey in a ml-calibrated cup, it won't be 44 ml because honey is much denser than water.
Always check your recipe. If it says "1.5 oz" for a dry ingredient like flour or sugar, use a scale. If it says "1.5 fl oz" or refers to a liquid, use your ml-calibrated measuring cup.
Real-world applications for 44.36 ml
Think about travel. The TSA (Transportation Security Administration) has that famous 3-4-1 rule. You can carry liquids in containers that are 3.4 ounces (100 ml) or less.
If you have a 1.5 oz bottle of expensive cologne, you’re well under the limit. In fact, you have less than half the allowed volume.
In medicine, this precision is even more vital. If a liquid medication dosage is 1.5 oz, a doctor will almost always write it as 45 ml or 44 ml to avoid any ambiguity. In a clinical setting, "ounces" are dangerous because they invite human error.
💡 You might also like: Half Brown Half Black Hair: Why This High-Contrast Look Is Actually Hard To Get Right
Practical steps for your next project
Stop guessing.
If you’re doing anything where the outcome matters—whether that's a chemistry experiment or a high-end cocktail—get a graduated cylinder or a high-quality jigger that has ml markings on the inside.
- For Cocktails: Buy a Japanese-style jigger. They usually have markings for 15 ml, 30 ml, and 45 ml. Use the 45 ml mark for your 1.5 oz pours.
- For Baking: Switch to a digital scale. Forget the ml conversion entirely and just aim for 44 grams for water-like liquids.
- For Medicine: Always use the syringe or dosing cup provided with the medication. Never use a kitchen spoon or a standard shot glass.
Basically, if you remember that 1.5 oz is roughly 45 ml, you'll be fine for 99% of life's situations. For that remaining 1%, remember the 44.36.
Check your equipment. Most cheap kitchen measuring cups are notoriously inaccurate, sometimes off by as much as 10%. If you really care about that 1.5 oz measurement, calibrate your cup by taring a scale with the empty cup and then adding water until the scale reads 44 grams. Mark that line. That's your true 1.5 oz.