Weight vs. Volume Explained

Have you ever received your package of fragrance oils and wondered why some of the bottles appeared more full than others? Perhaps you questioned why some of them were not filled all the way to the top. You may have even worried that you were shorted or that some of your bottles leaked. 

You are not alone! This is actually a very common question! 

So, why do some bottles appear more full than others? The answer lies in knowing the difference between weight and volume.

Today, we’re going deeper into the world of weights and volumes—exploring why understanding this distinction matters for product formulation and consistency.

Weight vs. Volume: What’s the Difference?

Fragrance oils are usually listed in ounces, milliliters, or grams.  Here at Indigo, we use ounces (and pounds) and we measure our fragrance oils by weight, not volume. 

• Volume is the space that the liquid takes up in the bottle. If we sold fragrance oils by volume, each bottle would be full to the top, regardless of how much that oil actually weighed. 

• Weight is about mass. It measures how heavy something is. It is similar to when a person steps on a scale. This measures weight (how heavy something is) and not how much room it takes up. When you order a fragrance oil by weight, you get a specific mass of that oil, regardless of how much space it takes up in the bottle.

Interesting Fact: the same volume of two different fragrance oils can weigh completely different amounts. 

Why? Because each oil has its own specific density, the relationship between its weight and volume. Even if poured into identical 1-ounce bottles, a light, airy citrus fragrance oil will weigh less than a rich, syrupy oil. So to get to that 1 ounce measurement, the citrus oil would appear fuller as it took more oil to get to that 1 oz. measurement. It takes less oil to reach 1 oz. of the heavier oil. This is why some of our customers notice that their bottles do not all look the same, and it is not an error.

We all know that every drop of fragrance oil counts when you are crafting your products whether that be soap, candles or other bath and body products. Precise measurements are needed for consistent results.

Why We Sell by Weight?

We measure our fragrance oils by weight, not volume, at IndigoFragrance—because weight is the gold standard for accuracy and consistency—two non-negotiable things when formulating products that need precise measurements.

Imagine you’re making a batch of perfume oil. The recipe is perfect, with 1 oz of a floral fragrance oil,  1 ounce of a thicker woody base fragrance, and a carrier oil to round it out. If we sold by volume, slight differences in the density of the oils would throw off your ratios and your finished product might not end up as expected.  

By selling by weight vs. selling by volume we ensure you get the same amount of fragrance oil every time, no matter its density.

This also explains the bottle mystery. The 1-ounce bottle of lightweight floral fragrance oil might look fuller than a 1-ounce bottle of heavier, denser oil because the denser one takes up less space. Neither bottle leaked, and you’re not being shorted—they both weigh exactly 1 ounce. It’s just physics at play.

 

Why Accurate Measurements Are Everything in Formulation

Anyone who deals with soap and perfume-making knows consistency truly matters.  It is important that your product is the same from one batch to the next. That’s where understanding weight vs. volume becomes your secret weapon.

By sticking to an oils actual weight, you lock in that batch to batch consistency. 

Fragrance Bottle Sizes

What can you expect when your fragrance oils arrive? The fragrance oils come in various sizes—1 oz, 2 oz, 4 oz, 8 oz or 16 oz, measured by weight. But because each oil’s density varies, the liquid level in those bottles won’t always look uniform. 

 A 4-ounce bottle of light, zesty lemon oil might nearly reach the top, while a 4-ounce bottle of a thick, resinous myrrh oil sits lower. It’s not about aesthetics—it’s about giving you the exact amount you paid for.

 

Wrapping It Up

So, the next time your fragrance oil arrives and the bottle levels catch your eye, you’ll know what’s happening. Weight vs. volume isn’t just a technical detail, it’s the foundation of accuracy in the fragrance world. At Indigo Fragrance, we’re committed to giving you what you paid for- regardless of how full the bottle may appear.

 

     We’ve covered the measurements so that you can focus on the magic!

Happy creating!