LotionMath vs Other Lotion Calculators
What separates a full emulsion formulator from a simple batch scaler
Search for "lotion calculator" and you will mostly find batch scalers — tools that take a percentage formula and output grams for a given batch weight. That is useful, but it is not formulation. Building a lotion from scratch means choosing the right emulsifier, matching your HLB, checking preservative coverage, and catching ingredient conflicts before you make a batch that fails.
LotionMath is a full emulsion formulator. This article explains what it does that other free tools do not, and where batch scalers are still the right choice.
At a Glance
| Feature | LotionMath | Lotioncrafter | MakingCosmetics | Generic batch scalers |
|---|---|---|---|---|
| Builds formula from scratch | ✅ | ❌ | ❌ | ❌ |
| Scales existing formula | ✅ (via BatchMath) | ✅ | ✅ | ✅ |
| O/W emulsion support | ✅ | ❌ | ❌ | N/A |
| W/O emulsion support | ✅ | ❌ | ❌ | N/A |
| HLB calculation | ✅ (two workflows) | ❌ | ❌ | ❌ |
| Ingredient compatibility warnings | ✅ (17 types) | ❌ | ❌ | ❌ |
| Preservative coverage display | ✅ (G+, G−, Y, M) | ❌ | ❌ | ❌ |
| PUFA-based antioxidant recommendation | ✅ | ❌ | ❌ | ❌ |
| Ingredient database size | 300+ | N/A | N/A | N/A |
| W/O emulsifier limits | ✅ per emulsifier | ❌ | ❌ | ❌ |
| QS-to-100 ingredient support | ✅ | ❌ | ❌ | ❌ |
| Free, no account | Yes | Yes | Yes | Yes |
What most lotion tools actually do
The majority of "lotion calculators" available for free online do one of two things:
- Batch scalers — you enter a formula in percentages and a batch weight in grams, and it multiplies. This is what SoapMath's BatchMath calculator handles.
- Ingredient sourcing pages — supplier sites (Lotioncrafter, Lotion Crafter, MakingCosmetics) have percentage-to-gram converters embedded in their product pages, which help you calculate how much of their specific ingredient to buy.
Neither of these tells you whether your formula will work, whether your emulsifier choice is right for your oil phase, whether your preservative covers all pathogen types, or whether two ingredients you picked will conflict.
BatchMath for scaling
LotionMath's four workflows
LotionMath has four separate formulation workflows depending on emulsion type and how you want to choose emulsifiers:
| Workflow | When to use |
|---|---|
| O/W Blend | Build an O/W emulsion and pick a single emulsifier by name (e.g., Emulsifying Wax NF, BTMS-50, Olivem 1000) |
| O/W HLB | Calculate the required HLB for your oil phase and blend two emulsifiers to hit it (e.g., span + tween combination) |
| W/O Blend | Build a water-in-oil emulsion — water phase limited by emulsifier type, oil phase dominant |
| W/O HLB | W/O emulsion built around target HLB rather than a named emulsifier |
Most beginner and intermediate formulators use O/W Blend with a named emulsifier. The HLB workflows are for formulators who want full control over their emulsifier system or who need to replace a discontinued emulsifier with an equivalent.
Compatibility warnings
The compatibility warning system is the most distinctive feature. When you add ingredients, LotionMath checks them against each other in real time. Warnings appear inline before you generate the formula.
- Charge conflicts — cationic conditioning agents (BTMS, cetrimonium) cannot be combined with anionic ingredients (SLS, anionic thickeners) without compatibility issues.
- Electrolyte-sensitive thickeners — Carbomer, Carbopol, and similar polymers collapse in the presence of salts. The calculator flags Carbomer + Sodium Benzoate, Carbomer + electrolytes, and similar combinations.
- pH incompatibility — some preservatives (Phenoxyethanol blends, Naticide) have effective pH ranges. The calculator warns when your ingredient combination would push pH outside the preservative's working range.
- Active ingredient stability — Vitamin C (L-Ascorbic Acid) is unstable at higher pH and conflicts with alkaline ingredients. The warning system flags destabilizing combinations.
- HLB mismatch — when using the HLB workflow, the calculator warns if your emulsifier's HLB is significantly off from your oil phase's required HLB.
- W/O water phase limits — each W/O emulsifier has a maximum water phase it can hold (typically 65–75%). Exceeding it produces a formula that will break or invert.
Preservative coverage
Every preservative added to the cool-down phase shows a coverage grid: G+ (gram-positive bacteria), G− (gram-negative bacteria), Y (yeast), and M (mold). Full coverage is marked ✅, partial coverage (one source with partial efficacy) is ⚠️, and no coverage is ❌.
This matters because no single broad-spectrum preservative covers all pathogen types perfectly. Phenoxyethanol, for example, is weak against gram-negative bacteria at low concentrations. Pairing it with a gram-negative booster (ethylhexylglycerin, caprylyl glycol) fills the gap. The coverage display makes this visible without requiring you to research each preservative independently.
Preservative effectiveness depends on pH and formula type
W/O emulsion support
W/O (water-in-oil) emulsions — cold creams, barrier creams, sunscreen bases, and rich body butters — are harder to formulate than O/W. The oil is the external phase, so water content is limited by what the emulsifier can hold. Get the water percentage wrong and the emulsion inverts or breaks.
LotionMath enforces per-emulsifier water limits in W/O mode. Beeswax + Borax, for example, can hold a maximum of 75% water phase. ABIL EM 90 is capped at 75%. Glycol Stearate is capped at 65%. The calculator prevents you from exceeding these limits and shows a live running total.
For Beeswax + Borax, the traditional cold cream system, LotionMath auto-distributes the beeswax and borax amounts based on your target emulsifier percentage — you do not need to calculate the 10:1 beeswax-to-borax ratio manually.
Pro Tip
What LotionMath does not do
LotionMath is a formulation planning tool. There are things it does not handle by design:
- Stability testing prediction — whether your formula will separate, discolor, or show microbial growth over six months cannot be calculated. Only laboratory testing answers that question.
- Rheology prediction — viscosity depends on shear rate, temperature, and manufacturing process in ways that cannot be predicted from an ingredient list alone.
- Sensory feel — the spreadability, skin feel, and absorption rate of your formula depend on manufacturing, not just formulation.
- IFRA fragrance compliance — fragrance safety at your specific usage rate needs IFRAMath, which verifies each component of your blend against 48 IFRA product categories.
When to use LotionMath vs BatchMath
| Situation | Right tool |
|---|---|
| Building a new lotion or cream formula | LotionMath |
| Choosing an emulsifier for a specific oil phase | LotionMath (HLB workflow) |
| Checking compatibility of ingredients you already have | LotionMath |
| Scaling a proven percentage formula to a different batch size | BatchMath |
| Converting between % and grams for a known formula | BatchMath |
| Checking preservative coverage of your current system | LotionMath |
| Formulating a W/O cold cream or barrier cream | LotionMath (W/O mode) |