How Much Oil in a Diffuser? Sizes and Drops, a Guide


So we’ve all been there, eagerly opening our brand new pretty diffusers, grabbing a handful of essential oils, and suddenly realizing you have no idea how much oil in a diffuser you should use! and could really benefit from knowing about sizes, drops, and a guide!

You might be wondering if you have to add more drops for less fragrant oils and maybe even reduce the drops for the more potent types of essential oils in your diffuser! 

In this article, I’m going to answer this question once and for all and give you a clear understanding of how much oil should go in a diffuser, what happens when the oil is too much, what’s the water and oil ratio that should go into a diffuser, and much more! 

Let’s get started first with the short answer, so you can start enjoying those blissful moments with your essential oils and diffusers straight away and know exactly how much water and drops of oil to use.  

How much oil in a diffuser? The general answer as to the amount of oil to use in a diffuser is around 3 -5 drops of essential oils per 100ml of water. Diffusers usually come in 200 ml to 1000 ml sizes. This is of course personal preference and will also depend on the oils you choose, plus the size of the room your diffuser is in. 

Ok, so now we’ve hit the quick answer, so you can start enjoying your diffuser and fragrant essential oils straight away, let’s start by taking a look at a quick little table which will give you all the details you need, before we take a more in-depth look. 

Many of us struggle with making sure our diffuser is being exactly what we want it to be! Which is filling our room with beautiful blends of essential oils. 

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Welcome to Willow Yard

This is a very common issue when using diffusers. Many of us ask questions such as why doesn’t my diffuser smell of anything? Is my room too big for my diffuser? Am I using enough essential oils? Why is my diffuser too overpowering and more! 

So lets start first by finding out a little more about the amount of oil you need to use in your diffuser. 

How much oil in an ultrasonic diffuser?

There are so many conflicting suggestions on the amount of oil you can use in your diffuser. 

We’ve all been there, leaning over our diffuser thinking that it doesn’t smell as intense as we would like it, or maybe it’s just far too powerful and overwhelming! 

We may be investigating the electrics, pulling out the instructions while pulling out our hair! 

So the definitive answer is that the amount of oil going into a diffuser depends partly on the capacity (size) of the diffuser as a quick guide. 

We will get on to the other reasons shortly, but first, let’s take a look below at a breakdown of how much oil can go into a diffuser based on the size of your diffuser. 

Diffuser Capacity (ml)No Drops of Oil
100ml3-5
200ml6-10
300ml11-15
400ml16-20
500ml21-25
1000ml30-50
Drops of oil for diffuser size table

Adjust the amount of oil in a diffuser for different types of essential oils

Do also remember that this is just a general guide and it could be that even 3 – 5 drops of some oils which are very potent, such as peppermint, eucalyptus, frankincense, tea tree or the more woody types such as spruce or cedar maybe a little too potent! 

The same could be said of the lighter more floral fragrances such as ylang ylang, geranium and rose that you may have to adjust the drops of oil you use in your diffuser, but this time, by adding a few more. 

The right amount of oil in your diffuser is down to you! 

Although 3 – 5 drops is the most usual amount of oil, it’s worth remembering that one of the most important things about any kind of aromatherapy is that it’s customized for you! 

It could be that you might enjoy stronger aromas of certain oils and not be so keen on others. 

This is where you can make your diffuser blend your own and the size of diffuser you find best for your use. 

For example, if you love the smell of lavender ( and who doesn’t!) you might have a 500ml diffuser so according to the general rule, you would be adding 22 -25 drops of lavender but you simply want it a little more intense! 

For more lavender loveliness, head over and check out the benefits of mixing lavender with ylang-ylang, or some ways to harness the benefits of lavender and tea tree. Also find out if your lavender oil has gone off, and how it can help you relax, in my specially curated list of 21 best oils for calm and relaxation!

Don’t worry, you can’t ‘break’ your diffuser by adding too much oil ( unless of course, you add enough to come over the waterline!) but that would be a considerable number of drops and bottles! 

I will let you know a little further into the article how many drops you are likely to get out of one bottle of oil and what to do if you have added too much oil. 

Ok so now we know that size IS important! Let’s do a little drilling down into how to find the size of your diffuser, so you can make sure you are adding the correct amount of oil. 

How do I find out the size of my diffuser 

As we’ve seen above, How much oil goes into a diffuser directly is based on the capacity of the diffuser or the capacity of water that can be held in your ultrasonic diffuser. 

So you might be wondering WHY the amount of oil in your diffuser is dictated by the water capacity? Let’s discover more. 

Why are essential oils added to water in my diffuser? 

The reason for this is because essential oils are exceedingly potent and should never be used without diluting them first. 

Diffusers use water as the ‘carrier’ as the water dilutes the oils in your diffuser. 

So according to the general standard, for every 100 ml diffuser, it’s recommended to add 3-5 drops of essential oil. 

Diffusers come in different sizes, which means the water holding capacity may also differ which will of course change the amount of oil that goes into the diffuser. 

However, thankfully, all of these different sizes of diffusers are in 100ml increments, so it makes it a little easier to calculate! So how do you find out the capacity of your diffuser, so you can make sure you are adding the proper amount of essential oil? 

blue diffuser pic
i just love this gorgeous turquoise on my diffuser!

How do I find out the capacity (size) of my diffuser? 

To find out the capacity of your diffuser, it will usually tell you in the product details if you purchased online. 

Some diffusers will also have the capacity printed on the packaging, or at the very least, the capacity in milliliters will be on your instruction pamphlet. 

So for example the smallest diffuser with a capacity of 100 ml will take 3-5 drops of oil, whereas the largest capacity of 1000 ml diffusers will take between 30 and 50 drops. 

Of course, this is a general guide, so do feel free to add more essential oil to your diffuser or less if you just feel like a hint of scent! 

Another tip to make sure you have the water and oil ratio right in your diffuser is to make sure you only fill your diffuser to the waterline. 

Add water to the waterline only 

Most brands will clearly show the maximum water capacity. Overfilling could cause it to overheat it or stop working altogether and also affects how the amount of oil in your diffuser blends with the water. This may also invalidate any guarantee you may have. 

Most diffusers have the water line inside the water reservoir or if they don’t, they will add a measuring cup to fill water and add to the reservoir. 

You can of course refer to the diffuser manual to find the recommended water level. 

Make sure that you don’t fill the diffuser with more than the recommended water capacity as this will affect how the oil blends with the water, and in worse cases the aroma diffuser may not run properly. 

Although there is no exact rule, the other main thing to take into account when you want to get exactly the right amount of essential oil drops to give off a glorious scent is the size of the area or room your diffuser is in.  

to find out how your diffuser can really help to support your immune system, head over and find out 14 of the best diffuser recipes for a healthy immune system

Does the size of the room make a difference to the amount of oil in a diffuser? 

There are many places you might want to plug in your diffuser and enjoy the relaxing aroma of essential oils. 

For example, you might want to know how many drops of oil to add to your diffuser if you are placing it in one of the following rooms: 

  • Bathroom 
  • Bedroom 
  • Home office
  • Children’s nursery 
  • Kitchen 
  • Dining room 
  • Lounge 
  • Summerhouse

As a guide, the above guide works well for a standard-sized room.

It makes sense that if your room is very large or maybe very small, to alter the drops accordingly. 

For example in a very large lounge or other space, it would give you a more intense aroma from your oils if you increase the amount 5 to 10 drops based on a standard 500-milliliter diffuser. 

For smaller rooms, you could decrease by 1 – 2 drops till you get just the right amount of sensory experience from your diffuser. 

So you might also be wondering when thinking about how oil to use in your diffuser, how many drops there are in each bottle! 

This can help you make sure you have enough of your favorite oil and get the right amount of drops. 

how many drops of oil
how many drops of oil in a diffuser?

Let’s look below and find out! 

How many drops of oil in an essential oil bottle?

Starting from the lower end, there are 200 drops or uses of essential oil in a 10ml bottle of essential oil.

This means that you can get 40(if 5 drops are used for every 100ml of water)-65 (if 3 drops are used for every 100 ml of water) uses or drops out of a 10ml essential oil bottle for a 100ml diffuser. 

With that being said, below is a quick breakdown of how many drops or how much use one can get from different ml of essential oil bottles for a 100ml diffuser. 

Volume (ml)No of DropsNo of Uses
5ml10020-33
10ml20040-65
15ml300100
30ml600200
120ml2400800

So before we finish this useful article on how much oil to use in your diffuser, you might be is there too much oil you can add to your diffuser? and what happens if you add too much oil to your diffuser?

What happens if I add too much oil into a diffuser 

Although the scent of essential oils is beautiful and gives a fabulous sensory experience, it can be a little overwhelming if you add too much.

This is of course far more noticeable in smaller areas such as a bathroom or other small room. 

It’s fairly easy to work out the oils which have a very strong aroma, right from the first smell from the bottle!  

Even when adding a tiny bit of the stronger smelling oils to a diffuser, it may make it too strong and too much essential oil for a confined space. 

The important thing to understand is that if you add too much oil it could lead to health issues to those who are breathing in the aroma. 

Those who are at high risks such as those who are sensitive to oils, such as children or people who have an allergy.

If you suspect that you’re having an allergic reaction to essential oil, stop using it immediately. Open your windows and clear the air.

If you aren’t suffering from an allergy and have simply added too much oil to your diffuser, simply follow the steps below. 

“If you suspect that you’re having an allergic reaction to essential oil, stop using it immediately. Open your windows and clear the air.”

What to do if you add too much oil into a diffuser?

After stopping the diffuser, empty the reservoir into two screw-top jars. 

Each jar will now have half the potency it had originally. So use those blends for those times you want a less intense aroma such as a background air freshener. 

Or you can add another couple of drops of oil to each to refresh the blend. 

Don’t worry at this point that it will be too potent as you’ve halved the solution so there’s room for another 1 or 2 drops! 

And to finish… 

So I hope that’s given you everything you need to know about how much oil to put in a diffuser and answered many of your other questions too! 

Remember the general rule of 3-5 drops per 100 milliliters and provided you don’t have allergies or any other kind of sensitivity to essential oils, you are good to go! 

Don’t forget to check out my other helpful articles for all you diffuser addicts out there! one of the commonest questions I’m asked is ‘Can You Sleep With a Diffuser On?‘ and many also ask me, ‘What Else Can I Put In My Diffuser, Besides Oil?’ and lots of beautiful blend advice. Also discover how One of my favorites’ Geranium Oil Blends Well With… 30 Oils, Recipes, and Uses.

This content has been checked and verified by a medical professional or aromatherapist The article has been reviewed by our editorial board and has been approved for publication in accordance with our editorial policy.

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