Two kilos to make tonight — and your formula's written in percents.
Enter your rows — ingredient, percent, phase — set the batch weight, and every gram lands at once: phase subtotals, bottles filled, leftover, cost per bottle. Everything stays in your browser.
Your formula (percents)
The batch
The pack
The numbers here are yours to check. This page does arithmetic on what you type — it cannot see your recipe, your equipment or your batch.
Want it to remember?
In MadeKeeper this same formula runs against your real shelf: each make consumes the exact grams of every ingredient from inventory, the bottles you fill set the unit count, and cost per bottle feeds the price coach. See for soap & body-care makers or poke around the live demo. $19/mo for the whole back office, kept for as long as you stay. The shop stays free for cost a piece and one fair — no product cap. The tax packet, Etsy and Square, and more fairs are the $19.
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The math this page runs, the check line it shows, and the numbers it deliberately leaves yours.
How do I convert lotion formula percentages to grams?
Each row is one multiplication: the percent divided by 100, times your batch weight. On a 500 g batch, 70% water is 350 g, 20% oils is 100 g, 5% emulsifier is 25 g, 1% preservative is 5 g, and a 4% cool-down phase is 20 g. That's the whole trick — the calculator just runs it on every row at once, subtotals each phase, and counts your bottles, so you're not walking the formula one ingredient at a time on a phone calculator.
How much emulsifier does a lotion formula need — and what's the 25% check line?
There's no single right number, which is why it's a setting here and not a constant. What the calculator does show is the common supplier rule of thumb: size the emulsifier at 25% of the oil phase. When your formula has an oil phase, that figure appears as a display-only check line — in the 500 g example the oils alone are 100 g, so the check lands at 25 g — exactly what a 5% emulsifier row gives you. One honest wrinkle: the subtotal on this page counts everything you filed under the oil phase, emulsifier included, so if your emulsifier rides there the check reads a little higher — treat it as the ballpark it is. It's there to compare against, not to obey; your emulsifier's own documentation beats the rule of thumb, and your rows are what actually gets weighed.
What preservative percentage should I enter?
The rate your preservative's supplier documents for it — that's the one number this page won't suggest, because it's different for every product and every formula. Enter it and the calculator does the arithmetic exactly as written: a 1% row on a 500 g batch comes out to 5 g. What that preservative can and can't do in your lotion is a question for its supplier's documentation and your own tested process, not for a scaling tool.
What happens if my percentages don't add up to 100?
The calculator says so, plainly — "totals 98.5%" — and then scales every row by its own percent anyway. It never silently normalizes, because a formula that's been quietly rescaled behind your back isn't your formula anymore. Whether you nudge the water phase up or run the batch a few grams short is your call, made with the real numbers in front of you.