The Inexact Science of a "Drop"
While it is a commonly used unit in aromatherapy, a "drop" from an essential oil bottle is not a standardized or scientifically accurate measurement. Numerous factors influence the size of each drop, leading to significant variations even from the same bottle over time. Relying solely on a drop count can lead to inconsistent blends, ineffective applications, or, in some cases, safety issues from over-concentration.
Factors that affect the size of a single drop include:
- Viscosity: The thickness of the oil plays a major role. Thinner, more fluid oils like lemon will produce smaller drops, while thicker, more viscous oils like myrrh or patchouli will create larger, heavier drops.
- Temperature: The temperature of the essential oil and the surrounding environment can alter its viscosity. Hotter temperatures make oils thinner, producing smaller drops, while colder temperatures make them thicker, leading to larger drops.
- Dropper Design: The size and design of the orifice reducer (the plastic insert) in the bottle varies by brand and batch, directly affecting the size of the drop dispensed.
- Dispensing Speed: How quickly or slowly you tilt the bottle can also influence the drop size. A slow, steady tilt generally produces a more consistent drop than a rushed one.
Converting 20 Drops to Standard Measurements
Despite the variability, a general industry rule of thumb is that 20 drops of essential oil is roughly equivalent to 1 milliliter (ml). However, this is an approximation and should only be used for small, non-critical applications where precision is not paramount. For more accurate measurements, especially when formulating topical products, it is better to measure by weight using a digital scale.
Approximate Drop Conversions:
- 20 drops ≈ 1 ml
- 60 drops ≈ 3 ml (often 1/8 teaspoon)
- 300 drops ≈ 15 ml (or 1/2 ounce)
Keep in mind that these are loose conversions. For example, studies have shown that 20 drops of different essential oils can weigh differently, with some experiments yielding weights between 0.3g and 1.05g. This demonstrates why measuring by drops is inherently unreliable for serious blending.
Why Accurate Dilution is Critical for Safety
For most topical applications, using essential oils “neat” (undiluted) is not recommended and can cause skin irritation or sensitization. Proper dilution is essential. Diluting with a carrier oil like jojoba, almond, or fractionated coconut oil ensures the essential oil is safely dispersed before being applied to the skin.
| Essential Oil Dilution Chart for Topical Use | Application | Dilution % | Total Volume | Approximate Drops (using 20 drops ≈ 1ml) |
|---|---|---|---|---|
| Facial Serums | 0.2 - 1.5% | 1 oz (30 ml) | 1–9 drops | |
| Body Massage Oil | 1.5 - 3% | 1 oz (30 ml) | 9–18 drops | |
| Bath & Body Products | 1 - 4% | 1 oz (30 ml) | 6–24 drops | |
| Spot Treatment | 4 - 10% | 10 ml | 8–20 drops | |
| Children/Sensitive Skin | 0.5 - 1% | 1 oz (30 ml) | 3–6 drops |
It is crucial to note that 20 drops, or approximately 1 ml, represents a significant concentration. For most body applications, a 2% or 3% dilution is standard, meaning 20 drops is likely more than you need for a single ounce of carrier oil. Always start with a lower dilution and perform a patch test before wider application.
Creating a Simple Essential Oil Roller Bottle
A common way to use diluted essential oils is in a roller bottle for targeted application. Here’s a simple recipe for a 5% dilution in a standard 10ml roller bottle, which is safe for most adults for spot treatment.
Ingredients:
- 10 ml roller bottle
- 10 drops of your desired essential oil(s) (e.g., lavender for calming, peppermint for headaches)
- Fractionated coconut oil or another carrier oil
Instructions:
- Add the 10 drops of essential oil to the clean roller bottle.
- Fill the rest of the bottle with your chosen carrier oil, leaving a small amount of space for the roller ball to fit.
- Snap the roller ball into place and secure the cap.
- Shake gently to mix thoroughly.
Practical Applications for Your Blends
Beyond topical use, understanding your measurements can help with other aromatherapy applications.
For Diffusers For a standard ultrasonic diffuser (typically 100-200ml capacity), a common practice is to add 5–10 drops of essential oil to the water. 20 drops would be too much for a single-use and could be overwhelming or potentially damage the diffuser. For a reed diffuser, a recipe might call for 20 drops of oil in a larger amount of carrier oil, mixed with alcohol to help it travel up the reeds.
For Household Cleaners Essential oils like tea tree, lemon, and eucalyptus are popular additions to natural cleaning sprays. A recipe for a 300 ml spray bottle might use around 50–100 drops of essential oil, mixed with water. In this case, 20 drops would represent a lower concentration for a less potent scent or cleaning power.
The Takeaway on Measurement
Ultimately, while 20 drops is often equated to 1 ml, the imprecision of this measurement means it should be used with caution. For simple, low-risk applications, a drop count is acceptable. However, for any topical use, especially on sensitive skin or when creating therapeutic blends, it is far safer and more effective to work with percentages and measure by weight. Consulting authoritative resources, such as the Tisserand Institute's essential oil dilution chart, can provide excellent guidance for safe blending.
Conclusion
While the concept of drops is convenient, relying on it as a precise unit of measurement is flawed. The volume and weight of 20 drops of essential oil will fluctuate based on the specific oil and dispensing method. For safe and effective aromatherapy, especially when applying topically, prioritize accurate measurement techniques like using percentages and measuring by weight. This mindful approach ensures you get consistent results while minimizing the risk of adverse reactions.
