How to Use LotionMath

Emulsion Calculator for Lotions, Creams & Barrier Products

LotionMath is an emulsion formulation calculator for oil-in-water (O/W) and water-in-oil (W/O) products — lotions, creams, serums, gels, and barrier creams. It organizes your formula into phases, tracks preservative coverage, detects ingredient conflicts, and generates a complete INCI-sorted results report.

Formula Types

O/W — Oil-in-Water Emulsion

Oil droplets dispersed in water. Lightweight, fast-absorbing, non-greasy. Standard for body lotions, facial moisturizers, and toners.

W/O — Water-in-Oil Emulsion

Water droplets dispersed in oil. Heavier, occlusive, water-resistant. Used for barrier creams and protective products. Uses a tiered primary/secondary emulsifier system.

Step-by-Step Formulation

Select Formula Type & Emulsifier

Select O/W or W/O at the top. Pick your emulsifier from the Oil Phase dropdowns. Recommended usage rates are pre-filled but can be adjusted.

Build Your Water Phase

Water is handled as QS (Quantity Sufficient) automatically. Add humectants (Glycerin), chelators (EDTA), and water-soluble thickeners or botanical waters here.

Build Your Oil Phase

Add emollients (carrier oils, esters), fatty thickeners (Cetyl Alcohol), and occlusives (Shea Butter). Typical O/W lotions use 5–20% total oil phase.

Cool-Down Phase (≤104°F / 40°C)

Add heat-sensitive ingredients like preservatives, fragrance, and actives (Vitamin C, peptides) once the emulsion has cooled to protect their effectiveness.

Intelligence Features

Viscosity Estimator

Predicts texture based on melting points, wax content, and thickeners:

Conflict Detection

LotionMath flags electrolyte sensitivity (Carbomer vs salts), pH conflicts (actives outside stability window), and charge conflicts (cationic vs anionic ingredients).

Preservative Coverage Tracker

Tracks protection across Gram-positive bacteria, Gram-negative bacteria, Mold, and Yeast. Ensures your formula is safely preserved for its target pH.

Tips for Success

Don't Under-Emulsify

Start with a proven emulsifier at its recommended rate. Under-emulsified lotions separate quickly.

Use the Wizard

Use the 'Help Me Pick' wizard for concern-matched oils and proteins, especially for hair conditioners.

Bench Test

If your lotion separates on freeze-thaw testing, increase emulsifier or add a co-emulsifier.

pH Before Preservative

Adjust your formula's pH first, then add the preservative at the correct temperature.

Frequently Asked Questions

Tip: Open LotionMath and try it now

The best way to learn is hands-on. Open LotionMath and start building your emulsion formula while following this guide.

Open LotionMath →