Blnded Bliss Soap Recipe & Lye Calculator

What this soap calculator does

Soap is what happens when fats meet lye. Stir oils together with sodium hydroxide (NaOH, for solid bars) or potassium hydroxide (KOH, for liquid and soft soap) and a reaction called saponification turns them into soap and glycerin.

The catch is that every oil needs a precise amount of lye to convert fully, This is called it's SAP value (saponification value). Use too much lye and you get a harsh, skin-stripping bar with leftover caustic in it. Use too little and you get a soft, greasy bar that can go rancid. And you can't eyeball it: swap one oil for another, or change a single percentage, and the right amount of lye changes with it.

This calculator does that math for you. Pick from a database of more than 100 oils, fats, butters, and waxes, set your batch up the way you want it, and it returns the exact lye and water weights to measure out as well as a read on how the finished bar will behave. It handles NaOH, KOH, and dual-lye blends, and you can save, print, export, or share any recipe you build.

How to use it

1. Set your total oil weight. This is the combined weight of all your fats, not the whole batch. Choose ounces, pounds, or grams with the display buttons.
2. Add your oils. Pick each oil and give it a percentage of the total. The percentages should add up to 100% — the tracker bar shows your running total and tells you how much you still need to add.
3. Choose a superfat. This leaves a small amount of oil unsaponified for a gentler bar. Most makers use 3–8%; 5% is a safe, common default.
4. Set your water. Pick how you want to define it: as a percent of your oils (simplest), as a lye concentration, or as a water-to-lye ratio. The live readout shows all three at once and warns you if your concentration drifts into an unsafe range.
5. Pick your lye type. NaOH for solid bars, KOH for liquid or soft soap, or a blend of both. If your KOH is the common 90%-pure flake, tick the “KOH is 90%” box so the weights come out right.
6. Add fragrance (optional). Enter a rate as a percent of oils or as ounces per pound. Use Define Scents to split a fragrance blend across multiple oils.
7. Calculate. You’ll get exact lye, water, and oil weights plus a set of quality scores. From there you can save the recipe to your browser, export a PDF or YAML file, print it, or copy a shareable link.

Reading the soap quality numbers

After you calculate, the summary predicts how your bar will perform based on the fatty acids in your oils. These are guides, not pass/fail grades — plenty of excellent bars sit a little outside the “recommended” window. Here’s what each one means:

• Hardness — how firm and long-lasting the bar is. Too high can be brittle and crack; too low stays soft and dissolves fast.
• Cleansing — how strongly the soap lifts oils. Higher cleansing feels more “squeaky,” but pushed too far it can be drying.
• Conditioning — how much the bar leaves skin feeling soft and moisturized rather than stripped.
• Bubbly — big, fluffy, airy lather (think coconut oil and castor).
• Creamy — dense, low, lotion-like lather (the kind tallow, lard, and butters give).
• Iodine & INS — two summary numbers that estimate overall hardness and longevity from the oil blend. Use them as a sanity check on the rest.

Superfat, water, and lye: the three dials

Most of the feel of a bar comes from how you set three things, and the calculator lets you move each one independently.

Superfat

Superfat (sometimes called a lye discount) is the slice of your oils deliberately left unconverted. A higher superfat means a more conditioning, gentler bar and a bigger safety margin against leftover lye — but go too high and the bar turns soft and short-lived. 5% suits most recipes; rich, oil-forward bars often run 6–8%.

Water

Water doesn’t end up in the finished bar — it just carries the lye and gets the reaction going, then evaporates during cure. More water gives you a thinner mix and more working time but a longer cure; less water sets up faster and harder. A lye concentration of roughly 28–40% covers most cold process soap, which is why the calculator flags anything above 40%.

Lye type

NaOH makes solid bars. KOH makes liquid and soft soaps. A dual-lye blend lets you nudge a bar’s texture — a touch of KOH can soften an otherwise rock-hard recipe. Consumer-grade KOH is usually about 90% pure, so check that box when it applies and the calculator scales the weight up accordingly.

Making tallow soap

Tallow is what Blnded Bliss is built on, so this is the part we know in our bones. Rendered beef tallow makes a hard, long-lasting, mild bar with a dense, creamy lather, and its fatty acid profile is close to what skin already produces — which is a big part of why old-fashioned tallow soap feels so gentle. It’s also a thrifty, low-waste fat: it puts a byproduct of meat to use instead of relying on imported palm oil.

How much tallow?

You can make a 100% tallow bar, and it’ll be hard and gentle — but on its own tallow can feel a little waxy and short on bubbles. Most makers blend it. A common starting point is around 70% tallow with 30% other oils: add coconut oil for cleansing and fluffy lather, and a small amount (5% or so) of castor oil to boost bubbles. Run a few versions through the calculator and watch the quality numbers move before you commit to a batch.

Superfat and working temperature

Tallow soap commonly runs a 5–8% superfat; a pure tallow bar often sits at the higher end. One quirk to plan for: tallow has a high melting point (roughly 95–105°F), so melt it fully and soap a touch warmer than you would with softer oils, or you’ll get false trace as the tallow re-solidifies.

Swapping fats and curing

Beef, sheep, deer, and goat tallow are close substitutes for one another — just recalculate the lye whenever you swap, since each has its own SAP value. Lard behaves similarly but gives a slightly softer, even creamier bar. However you blend it, cure your bars 4–6 weeks (longer makes them harder and milder), and start with fresh, clean tallow to avoid the orange spots that signal rancidity down the line.

Frequently asked questions