HLB Values Explained: How to Pick the Right Emulsifier Blend for Your Formula

Every stable emulsion starts with a number most formulators learned in a hurry and never fully trusted. HLB — hydrophilic-lipophilic balance — sounds simple on paper, but picking the right value (and the right emulsifier combination to hit it) is where a lot of “why won’t this cream stop separating” problems actually begin.

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Here’s what HLB really measures, how to calculate a target for your oil phase, and how to blend two emulsifiers to land on that number precisely.

What HLB Actually Measures

HLB is a scale from 0 to 20 that describes how hydrophilic (water-loving) or lipophilic (oil-loving) a surfactant molecule is. Low HLB values (roughly 3–6) indicate emulsifiers that favor oil — good for water-in-oil (W/O) emulsions. High HLB values (roughly 8–18) favor water — good for oil-in-water (O/W) emulsions, which is what most lotions, creams, and serums are built on.

The scale isn’t just theoretical. Every oil, butter, and ester in your formula has a required HLB — the HLB value at which an emulsifier system will most effectively keep that specific oil phase dispersed in water. Get the emulsifier blend’s HLB close to the oil phase’s required HLB, and you get a stable emulsion. Miss it by a wide margin, and you get separation, creaming, or a product that looks fine on day one and breaks by week three.

Calculating Your Target HLB

Most formulas use more than one oil, butter, or ester — and each has its own required HLB. To find the target HLB for your whole oil phase, calculate the weighted average based on how much of each oil is in your formula:

Target HLB = Σ (required HLB of ingredient × % of ingredient in oil phase)

For example, an oil phase that’s 60% ingredient A (required HLB 8) and 40% ingredient B (required HLB 12) has a target HLB of:

(0.60 × 8) + (0.40 × 12) = 4.8 + 4.8 = 9.6

That 9.6 is the number your emulsifier blend needs to hit.

HLB Scale (0–20)

0
Oil-loving (W/O)
20
Water-loving (O/W)

5 10 15

Target HLB 9.6 your oil phase’s required blend point

Emulsifier A HLB 4.3
Emulsifier B HLB 15

Blending Two Emulsifiers to Hit a Target

You’ll rarely find a single emulsifier with exactly the HLB you need — which is exactly why blending exists. Combining a low-HLB and a high-HLB emulsifier lets you dial in almost any value in between, and blended systems are often more effective at stabilizing an emulsion than a single emulsifier at the same average HLB.

The blending math works the same way as the target HLB calculation, solved in reverse:

% of high-HLB emulsifier = (Target HLB − Low HLB) / (High HLB − Low HLB)

So if you’re blending Emulsifier A (HLB 4.3) and Emulsifier B (HLB 15) to hit a target of 9.6:

(9.6 − 4.3) / (15 − 4.3) = 5.3 / 10.7 ≈ 49.5%

That means roughly 49.5% Emulsifier B and 50.5% Emulsifier A, by weight of total emulsifier.

Where Formulators Go Wrong

Mistake	Why It Hurts Stability
Using a single emulsifier “close enough” to target HLB	Single-emulsifier systems are more prone to phase separation under temperature stress than blended systems, even at the correct average HLB
Ignoring required HLB of minor ingredients	A 2–3% ester with a very different required HLB than the rest of the oil phase can shift your target more than expected
Not accounting for electrolytes or actives	Salts, acids, and certain actives can shift effective HLB requirements and destabilize an otherwise correct blend
Skipping stability testing after hitting target HLB	HLB gets you close — freeze-thaw and heat/cool cycling confirm you’re actually stable

The Takeaway

HLB targeting isn’t a guarantee of stability, but it’s the single most reliable starting point for building an emulsion that has a real chance of staying stable through testing. Calculate your oil phase’s required HLB, blend emulsifiers to hit that target, and then validate with proper stability protocols before you scale.

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Skip the manual math — our free HLB Calculator computes target HLB and emulsifier blend ratios automatically from your formula’s ingredient list.