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Calculators

Lotions & creams

A lotion is written as a list that totals 100 % of the finished product, with the water phase making up whatever is left. Change the butter and the water gives up the difference by itself. A formula that totals 98.6 % is refused rather than scaled, because that means a line was mistyped and every mass weighed from it would be wrong while looking fine.

The formula

One ingredient can be marked q.s. — it takes whatever is left to reach 100 %. Conventionally the water.

Batch

fill in the formula

Matching the emulsifiers

Required HLB is a published property of each oil and differs between sources by a point or more. Take it from your supplier’s data, and treat a match as a starting formulation rather than a specification.

Calculated at soapformulator.com, every value sourced. Check the figures against your own scale.

The formula, and where it comes from 
q.s.       = 100 − Σ(stated percentages)
massᵢ      = batch × percentᵢ ÷ 100

HLB_blend  = Σ(massᵢ × HLBᵢ) ÷ Σmassᵢ
f_high     = (HLB_required − HLB_low) ÷ (HLB_high − HLB_low)
  • Cosmetic formulations are written as percentage w/w of the finished product, totalling 100 %. Batch quantities are the percentage scaled to the batch mass: massᵢ = batch × percentᵢ ÷ 100.
  • The convention "q.s. ad 100" (quantum satis — as much as suffices) marks the ingredient, conventionally the water phase, that makes the formula up to 100 %. — Only one ingredient can be q.s.; two would leave the split between them undefined.
  • Usage rates are the supplier’s, from the ingredient’s own technical data sheet, and the range is a property of that material rather than of this calculator. — A rate inside its range is not a safety assessment. Preservative efficacy depends on the whole formula’s pH, water activity and packaging, and only a challenge test demonstrates it.
  • W. C. Griffin, "Classification of Surface-Active Agents by HLB", Journal of the Society of Cosmetic Chemists 1 (1949) 311–326; and "Calculation of HLB Values of Non-Ionic Surfactants", JSCC 5 (1954) 249–256. — Defined for non-ionic surfactants only. An ionic or polymeric emulsifier has no HLB in this sense.
  • The HLB of a blend is the mass-weighted mean of its components’ HLB values: HLB_blend = Σ(wᵢ × HLBᵢ) ÷ Σwᵢ. This additivity is the property that makes blending to a target possible and is stated in Griffin (1954).
  • The required HLB of an oil is determined experimentally and published in supplier and handbook tables; the required HLB of a mixed oil phase is the mass-weighted mean of the components’ values. — Published required-HLB values for the same oil differ between sources, often by a point or more, and depend on whether the emulsion is oil-in-water or water-in-oil. Treat a match as a starting formulation, not a specification.

Why the phases matter

The phase is the manufacturing order, and it is where a first lotion goes wrong. Heat the water phase and the oil phase separately to about the same temperature, combine them with shear, then let it fall below 40 °C before the cool-down goes in. Preservatives and fragrance belong there because heat destroys several of them.

On preservatives

Anything with water in it needs one, and a rate inside its supplier’s range is not a demonstration that it works. Efficacy depends on the whole formula’s pH, its water activity and its packaging, and only a challenge test shows it. This page checks the rate; it cannot check the preservation.

Common questions

It says my percentages do not total 100.
Mark one ingredient q.s. and it will take the balance. Without one, the total has to be right, because a formula that is close is a formula with a typo in it.
Where do I find a required HLB?
Supplier data sheets and emulsifier handbooks publish them per oil. We do not carry a table, because published values for the same oil disagree between sources and repeating one without its source is the thing this site exists not to do.
Why will it not take my emulsifier?
HLB is defined for non-ionic surfactants. An ionic or polymeric emulsifier works by charge or by rheology instead, so it has no HLB in this sense and averaging it into a blend would produce a number describing a different blend.
It matches. Will it be stable?
A matched HLB is necessary, not sufficient. Process, order of addition, shear, electrolytes and pH decide as much, which is why this says the ratio is right and never that the emulsion will hold.

Goes well with

All tools
Oil & butter reference Saponification values, iodine, fatty acids — as published ranges with the source on every row
Fragrance & allergen check IFRA load by product type and EU/Canada allergen declarations from supplier sheets

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