Calculating Percentage of 10% DHEAS Solution for Dropper Formulation (50 mcg/drop)

Asked by: homonesdress On: December 28, 2017 Product Type: Cosmetics Answered

Question

How do I calculate the percentage of a 10% DHEAS solution needed in a formulation for a dropper bottle to ensure each drop contains 50 mcg of pure DHEAS? The calculation should account for the weight of a single drop from the specific dropper being used.

Answer

To calculate the amount of 10% DHEAS solution needed in your formulation for a dropper bottle, aiming for 50 mcg of pure DHEAS per drop, you first need to determine the weight of a single drop from your specific dropper.

Let:

  • W_drop = Weight of one drop in grams.
  • Target pure DHEAS per drop = 50 mcg = 0.00005 grams.
  • DHEAS solution concentration = 10% (or 0.10 as a decimal).

The amount of pure DHEAS in a drop is the weight of the drop multiplied by the percentage of the 10% DHEAS solution in the formulation, multiplied by the concentration of DHEAS in that solution.

Amount of pure DHEAS = W_drop * (Percentage of 10% DHEAS solution / 100) * 0.10

We want this to equal 0.00005 grams:
W_drop * (Percentage / 100) * 0.10 = 0.00005

Solve for Percentage:
Percentage = (0.00005 / (W_drop * 0.10)) * 100
Percentage = (0.00005 / (0.1 * W_drop)) * 100
Percentage = (0.0005 / W_drop) * 100

So, the formula to calculate the percentage of the 10% DHEAS solution to add to your base formulation is:

Percentage of 10% DHEAS solution = (0.0005 / W_drop) * 100 %

Where W_drop is the weight of one drop in grams.

Steps:

  1. Carefully measure the weight of one drop from your dropper bottle in grams. You can do this by weighing the empty bottle, adding a known number of drops (e.g., 10 or 20), weighing the bottle again, finding the total weight of the drops, and dividing by the number of drops.
  2. Plug the measured W_drop value into the formula above to get the required percentage of the 10% DHEAS solution in your final formulation.
  3. Prepare your formulation using this calculated percentage of the 10% DHEAS solution mixed with your base.

For example, if one drop weighs 0.02 grams:
Percentage = (0.0005 / 0.02) * 100 % = 0.025 * 100 % = 2.5 %
This means that in your total formulation, 2.5% by weight should be the 10% DHEAS solution.

Once you have measured the weight of one drop, feel free to share it, and I can help you calculate the exact percentage.

Answer Update
Updated Review: May 2026

This section was added after reviewing the original answer against current product availability and formulation knowledge at the stated point in time.

Update 2026-05-24: The calculation in the original answer is still correct if the 10% DHEAS solution means 10% w/w pure DHEAS. For a target of 50 mcg pure DHEAS per drop, each drop must contain 0.00005 g pure DHEAS, so it needs 0.00005 / 0.10 = 0.0005 g of the 10% DHEAS solution. Therefore:

% of 10% DHEAS solution in the formula = (0.0005 / W_drop) × 100

where W_drop is the average weight in grams of one drop from the actual finished formula using the actual bottle/dropper.

Please do not use a generic drop size. Weigh 10–20 drops from the final formula, divide by the number of drops, and use that average. Re-check after changing the base, because viscosity, surface tension, bottle/dropper design, fill level, angle, and squeezing force can change drop size. For example, if the measured drop weight is 0.02 g, the required 10% DHEAS solution remains 2.5% w/w.

Also, DHEAS/dehydroepiandrosterone sulfate is hormone-related. Before using it in a cosmetic or consumer product, please confirm the current regulation in the target market, safety assessment, permitted claim scope, stability/uniformity in the formula, and suitability for the intended user group.

Tags

Amount Calculation Usage Percentage Solution Serum Weight and Volume