Everything a formulator needs to know about Hydrophilic-Lipophilic Balance — from the theory behind the number to calculating your own oil phase.
Lotions separate. Creams break. Conditioners go grainy. Almost every stability failure in an emulsion-based product traces back to one root cause: the emulsifier system wasn’t matched properly to the oil phase. The HLB method exists to solve exactly that problem — and it’s been doing so since 1949.
This guide covers how HLB works, how to calculate it for a mixed oil phase, how to blend emulsifiers to hit your target, and where the system has real limits that formulators need to respect.
What HLB Actually Measures
HLB stands for Hydrophilic-Lipophilic Balance. It’s a number assigned to a surfactant that describes how much of the molecule is water-loving versus oil-loving. William C. Griffin developed the method in 1949 for nonionic surfactants, and despite decades of more sophisticated models, it remains the most practical starting point in everyday formulation work.
The scale runs from 0 to 20. A molecule with a very low HLB is strongly oil-loving — it will preferentially sit in the oil phase and stabilize water-in-oil emulsions. A molecule with a high HLB is water-loving — it stabilizes oil-in-water emulsions. The midrange is where things get more nuanced.
The HLB method applies to nonionic surfactants. Attempts have been made to extend it to ionic and silicone surfactants, but with variable success — treat those extensions as a rough starting point only, not a reliable map.
Required HLB: What Your Oil Phase Needs
Every oil, wax, and lipid ingredient in your formula has a “required HLB” — the emulsifier HLB value at which that ingredient is most stably emulsified. These values are determined experimentally and are available from ingredient suppliers and published literature. They’re approximate, typically varying by about ±1 unit.
Here are required HLB values for some of the most common oil-phase ingredients:
| Ingredient | Required HLB | Best for |
|---|---|---|
| Mineral Oil | 10–12 | O/W |
| Beeswax | 9–11 | O/W |
| Cetyl Alcohol | 15–16 | O/W |
| Stearic Acid | 17 | O/W |
| Coconut Oil | 6–7 | W/O |
| Isopropyl Myristate | 11–12 | O/W |
| Lanolin | 12 | O/W |
| Petrolatum | 7–8 | W/O |
| Shea Butter | 6 | W/O |
Calculating the Required HLB of a Mixed Oil Phase
Most real formulas don’t have a single oil — they have a blend. To find the required HLB for your entire oil phase, you weight each ingredient’s required HLB by its proportion of the total oil phase.
Mineral Oil 40% req. HLB = 11
Shea Butter 35% req. HLB = 6
Cetyl Alcohol 25% req. HLB = 15
// Weighted calculation
(0.40 × 11) + (0.35 × 6) + (0.25 × 15)
= 4.4 + 2.1 + 3.75
= Required HLB = 10.25
Your emulsifier system should deliver an HLB close to 10.25 to stabilize this particular oil phase. Now you need to blend emulsifiers to hit that number.
Blending Emulsifiers to Hit Your Target
Emulsifier HLB values blend linearly — which makes the math straightforward. If you’re using two emulsifiers, you calculate their weighted average the same way you calculated the oil phase required HLB.
// Target HLB = 10.25, total emulsifier = 5%
Let x = fraction of Tween 80
(x × 15) + ((1-x) × 4.3) = 10.25
15x + 4.3 − 4.3x = 10.25
10.7x = 5.95
x = 0.556 → 55.6% Tween 80 / 44.4% Span 80
// In a 5% emulsifier blend:
Tween 80: 2.78% Span 80: 2.22%
A Practical Formulation Process
List every ingredient in your oil phase. Include oils, waxes, butters, fatty alcohols, and silicones. Pull the required HLB for each from supplier data sheets or literature.
Calculate the weighted required HLB for your entire oil phase using each ingredient’s percentage contribution.
Select a high-HLB and a low-HLB emulsifier pair. Widely used pairs include Tween 80 / Span 80, Polysorbate 60 / Sorbitan Stearate, and Ceteareth-20 / Glyceryl Stearate. Choose based on your skin-feel and regulatory requirements.
Calculate the blend ratio to match your required HLB. Use the linear blending formula above.
Make a small stability series. Prepare 3–5 batches spanning your target HLB ± 1.5 units. Observe stability at 4°C, 25°C, and 45°C over four weeks. The most stable formulas cluster around your true required HLB.
Where HLB Falls Short
HLB is a powerful starting point — not a complete formulation system. Several factors affect emulsion stability that HLB does not account for:
Emulsifier concentration
HLB tells you nothing about how much emulsifier to use. Too little and the emulsion breaks regardless of how well-matched the HLB is. Too much and you affect texture, skin feel, and cost. Concentration must be determined empirically, typically starting in the 2–6% range for the total emulsifier system.
Temperature and processing
The required HLB of an oil phase can shift with temperature. Processing temperature, mixing order, and homogenization speed all influence the final emulsion structure in ways that HLB calculations cannot predict.
Ionic strength and pH
Salt concentration and pH affect nonionic surfactant behavior more than their HLB values suggest. Formulas intended for high-electrolyte environments (like some rinse-off products) may behave differently than their HLB-based prediction.
Use the FormulaAlchemy HLB Calculator
Rather than running these calculations by hand, the FormulaAlchemy HLB Calculator lets you input your oil phase ingredients, enter their concentrations, and get an instant required HLB value for the blend. You can then compare it against your chosen emulsifier system and adjust until the values align.
The calculator is free and designed for working formulators — no account required to run a calculation.
Calculate your HLB in seconds
Enter your oil phase, get your required HLB, and align your emulsifier system — all in one free tool built for cosmetic and industrial formulators.
Open the HLB CalculatorThe Short Version
HLB is a number assigned to nonionic emulsifiers that describes their preference for water over oil. Each oil-phase ingredient has a required HLB. Match your emulsifier blend’s HLB to your oil phase’s required HLB and you have a stable starting point for your emulsion. Adjust with bench testing, because concentration, temperature, and formulation complexity all affect the final result in ways the number alone can’t capture.
Learn it once and it speeds up every emulsion you formulate after that.
