Buzz
I recently upgraded my kitchen scale. The new model includes all the features I desired, with negative tare being a major improvement. However, it also comes with two unnecessary features: 'milliliters' and 'fluid ounces' settings, which are utterly pointless.
A scale, by definition, measures weight. I value that my scale can weigh items in grams, which I frequently use, or in ounces. These units measure weight. (Technically, grams measure mass, but on a kitchen scale on Earth, this difference is negligible.)
Conversely, milliliters and fluid ounces measure volume. For example, a measuring cup contains eight fluid ounces, and a standard disposable water bottle holds 500 milliliters. These measurements indicate the capacity of the container.
Understanding the volume of an object doesn't reveal its weight. For instance, if you replace the water in your bottle with Everclear, maple syrup, olive oil, sand, molten lead, or helium, the weight will differ significantly. This is why distinct units for volume and weight exist—they measure entirely different properties.
How does my scale claim to measure volume?
What exactly is the fluid-ounces feature attempting to achieve? Essentially, it weighs the item placed on it and assumes it has the density of water. I tested this by measuring a fluid ounce of water using a small measuring cup from a cough syrup bottle. The scale displayed 1.0 fluid ounces, 1.0 ounces, 29 milliliters, and 29 grams.
This makes sense—water has a density of 0.997 g/mL, meaning 0.997 grams of water occupies 1 milliliter of space. Rounded off, one gram is approximately equal to one milliliter, and one fluid ounce is roughly equivalent to one ounce by weight. If a recipe calls for four fluid ounces of water (half a cup), you can simply weigh out four ounces. There's no need for a 'fluid ounces' setting; standard weight measurements suffice.
When measuring water or similar substances, the fluid ounce and milliliter settings are unnecessary—they merely repeat what the standard ounce and gram settings already indicate. However, for substances with densities different from water—such as alcohol, oil, or syrup—these settings are not just redundant but potentially harmful. They can result in incorrect measurements, ruining your recipe.
What impact does this have in practical scenarios?
To test this, I measured one 'fluid ounce' of whiskey and one 'fluid ounce' of Log Cabin maple-flavored pancake syrup.
Alcohol is less dense than water, with a density of 0.789 g/mL. This makes it lighter than water, which is why mixed drinks need to be stirred—otherwise, the alcohol will rise to the top. My inexpensive whiskey was 90 proof (45% alcohol), so its density is higher than pure alcohol but still much lower than water.
On the other hand, syrup is denser than water because the dissolved sugar increases its weight without significantly increasing its volume. If you've ever made simple syrup, you know this: combining one cup of water with one cup of sugar results in about one and a quarter cups of syrup, even though it contains the full weight of both ingredients. Pancake syrup has even more sugar, making it much heavier than water.
The image at the top of the page displays my findings. Both cups were measured by the scale as containing one 'fluid ounce' of liquid, but their volumes are clearly different. Using a small medication cup, I found that the whiskey (left) measures 36 milliliters, or 1.22 fluid ounces, while the syrup (right) measures 22 milliliters, or 0.74 fluid ounces.
If you were preparing a mixed drink for four people and opted to use your scale instead of a jigger to measure six fluid ounces in total (1.5 ounces per person), the drinks would end up significantly stronger than intended—each person would receive 1.83 ounces.
Conversely, if you were baking a cake that requires fluid ounces of maple syrup and relied on your scale rather than a measuring cup, you'd only add 2.55 fluid ounces of syrup. The cake would lack the intended sweetness.
(I’m aware the maple cake recipe specifies 'ounces,' but the British version lists 100 milliliters, approximately 3.4 fluid ounces. I also factored in the density of real maple syrup, 1.37, for my calculations, though it’s close to the 1.31 density of the imitation syrup I tested. This is just in case any of my former chemistry professors are reviewing my work.)
Syrup and alcohol are extreme cases, which is why I selected them. Here are a few other common liquids that can skew your measurements:
Oils are slightly less dense than water (0.917 mg/mL for olive oil)
Milk is marginally denser than water (1.04 mg/mL)
Peanut butter is somewhat denser than water (1.1 mg/mL)
Honey is significantly denser than water (1.4 mg/mL)
What’s the best approach? If you’re measuring water, any setting on your scale will suffice. However, for other liquids, stick to volume-based measurements. Use a measuring cup, a jigger, or even a tablespoon (which equals half a fluid ounce) for accuracy.
