How Do I Calculate Fragrance Oil for Soy Wax?

The formula, and the two numbers it needs

Fragrance load on CSI product pages is a percentage of total wax weight. So the calculation is one multiplication: oil in grams = wax in grams × load. Two hundred grams of wax at 8% is 200 × 0.08 = 16 g of oil, and the finished candle weighs 216 g. One hundred and fifty grams of wax at 10% is 15 g. Five kilograms of wax at 8% is 400 g. There is no hidden step, no conversion factor and nothing that changes with the wax grade.

What changes with the grade is the ceiling you are allowed to put into the formula. Luxury Soy Wax CSI 464 states up to 10% of total wax weight. Luxury Soy Wax Chunks states up to 13%, with 8% as a starting point and 10% as its recommendation. Premium Coconut Soy CSI 468 states up to 13%. Eco Soy CSI 400 does not publish a fragrance ceiling — ask on WhatsApp rather than assuming it matches another grade.

The oil has its own limit, printed on its own page, and it can be lower. Lavender Fragrance Oil gives 6–10% for candles. Dark Vanilla gives 6–10%. Citrus Lemon gives 6–10%. Japanese Cherry Blossom gives a wider 6–13%. Some pages, British Rose among them, publish a flashpoint (192°C) and vanillin content (0%) but no candle percentage at all — in that case the wax page is your only stated limit. Where both publish a figure, the lower one governs, and it goes into the formula as your load.

At ₹3.07 a gram for British Rose at 1 kg pricing, 16 g is ₹49.09 and 12 g is ₹36.82 — so the whole argument between 8% and 10% on a single candle is worth a few rupees. The reason to get the arithmetic right is not the money on one jar. It is that a wrong percentage repeated across a festive batch is the difference between a range that ships and a range that seeps, and you cannot tell which you have poured unless the numbers on the batch card are real.

Percentage of what? The one ambiguity that ruins the sum

There are two conventions in common use. The first, and the one every CSI page means, is percentage of wax weight: the oil is a proportion of the wax you weighed, and the finished candle is heavier than the wax by exactly the oil you added. The second is percentage of the finished candle, where the oil is a proportion of the total poured weight and the wax is what is left over.

Take the same physical candle: 200 g of wax and 16 g of oil, 216 g poured. Read as a percentage of wax it is 16 ÷ 200 = 8.00%. Read as a percentage of the finished candle it is 16 ÷ 216 = 7.41%. Nothing about the jar changed; only the sentence you write in your notes. The gap looks trivial at 8% and stops being trivial near a ceiling, which is exactly where people work when they are chasing throw.

The direction of the error is always the same and always unhelpful. If you apply a wax page’s ceiling to the finished-candle convention, you pour more oil than the page allows. Thirteen per cent of the finished candle is 14.94% of wax weight — above the 13% maximum stated for Luxury Soy Wax Chunks and CSI 468, and half again over the 10% stated for CSI 464. Ten per cent of the finished candle is 11.11% of wax, which quietly puts a CSI 464 candle over its stated maximum.

Converting between the two conventions

If you have a percentage of the finished candle and you need the wax-weight figure CSI pages use: wax% = candle% ÷ (1 − candle%). Going the other way: candle% = wax% ÷ (1 + wax%). Both come straight out of the definitions — the only difference between the two denominators is the oil itself.

Read the last three rows as a warning label rather than as options. They are what happens when a recipe from a forum, a supplier in another country or an old notebook uses the other convention and you apply a CSI ceiling to it. If a number arrives without its convention attached, ask which weight the percentage is of; if nobody can tell you, treat it as the finished-candle version, because that is the assumption that keeps you under the ceiling rather than over it.

Grams, never millilitres

Fragrance oils are sold by weight — CSI’s packs are 15 gm, 50 gm, 100 gm, 500 gm and 1 kg — and every load figure on every wax and oil page is a percentage of a weight. A beaker measures volume. The two are only the same number if the liquid happens to weigh exactly one gram per millilitre, and fragrance oils are blends whose density depends entirely on what is in them. CSI does not publish a density or specific gravity for its oils, so this page will not give you a millilitre-to-gram factor; weigh the oil and the question disappears.

The size of the error is easy to bound even without a density. Suppose a beaker reading is off by five per cent in either direction against the scale: on a 15 g dose that is 0.75 g, and across fifty candles it is roughly 37.5 g of oil either bought and not used or used and not counted — ₹56.76 at British Rose 1 kg pricing if you are over, and an unexplained weak batch if you are under. That figure is illustrative arithmetic about measurement error, not a claim about any particular oil.

Two more volume traps. Drops are not a unit: drop size depends on the bottle neck, the oil and the temperature. And a silicon measuring beaker (₹300.00) is genuinely useful for dyes, cleaning solvent and decanting — one reviewer above notes that CSI’s liquid dye is concentrated enough that a small amount gives a pastel shade, which is a volume tool doing a volume job — but it is the wrong instrument for the one ingredient whose limit is published as a weight.

The jar’s fill capacity is a total, not a wax weight

This is the step most calculations skip. The Clear Glass Jar with Golden Lid page gives a fill capacity of 150 g; the Ceramic Jar page gives 180 g; the Shot Glass Jar page gives 130 g; the Clear Glass Votive Jar is a 70 g fill; Tin Containers are 85 g and 135 g. Those are poured weights — wax plus oil. Pour 150 g of wax into a 150 g jar and then add 12 g of oil and you have 162 g of candle going into a 150 g space.

Work backwards instead. Wax = fill ÷ (1 + load), and oil = fill − wax. For a 150 g fill at 8%: wax = 150 ÷ 1.08 = 138.89 g, oil = 11.11 g. At 10%: wax = 136.36 g, oil = 13.64 g. The same two lines size every container you sell.

Two practical notes. Leave a little headspace rather than pouring to the stated capacity exactly — the fill figure is what the container holds, not a target to beat. And do not chase the last decimal: 138.89 g of wax is 139 g on a bench scale, and the load moves from 8.00% to 8.63% if you dose 12 g against it, which is inside any sensible tolerance. Precision matters near a ceiling and nowhere else.

Four worked examples, from one jar to fifty

Example 1 — one 200 g test candle at 8%

Wax 200 g of CSI 464 (₹101.48 at ₹507.40/kg), oil 200 × 0.08 = 16 g of British Rose (₹49.09), wick an Eco C1 at ₹5.90. Materials ₹156.47 before the jar; poured weight 216 g. This is the unit the whole CSI soy series costs in, so any figure you see quoted per candle across these guides is this jar.

Example 2 — a five-jar test round in 150 g jars at 10%

Work from the jar. Wax per jar 136.36 g, oil 13.64 g. Melt once for all five: 681.82 g of wax — call it 682 g — and dose 68.18 g of oil into the pot in one weighing. Wax ₹345.95, oil ₹209.18, and with wicks and jars the round is ₹1,056.64. Dosing the melt rather than the jar is the whole point: five separate 13.64 g weighings invite five separate rounding decisions.

Example 3 — fifty 200 g candles at 10%

Wax 50 × 200 g = 10 kg exactly, which is one CSI 464 10 kg pack at ₹5,074.00. Oil 10,000 × 0.10 = 1,000 g, which is one British Rose 1 kg pack at ₹3,068.00. Wicks 50 × ₹5.90 = ₹295.00. Materials, jars aside: ₹8,437.00. Round batch sizes like this are worth engineering deliberately, because they turn a purchase list into whole packs instead of awkward part-packs.

Example 4 — using a 1 kg pack of wax exactly

One kilogram of wax at 8% takes 80 g of oil (₹245.44) and yields 1,080 g of candle — 7.2 jars at a 150 g fill, so seven full jars and a remainder. At 10% it takes 100 g (₹306.80) and yields 1,100 g, or 7.3 jars. Scaling up: a 5 kg pack at 8% is 36.0 jars and a 10 kg pack is 72.0. Plan the remainder as a tester or a votive rather than discovering it at eleven at night with one jar left over.

Rounding: the quiet way a recipe climbs past its ceiling

Scales read in whole or half grams, and oil figures rarely land there. A 130 g shot glass at 8% wants 9.63 g of oil against 120.37 g of wax. Round that to 10 g and the load becomes 8.31% — still fine. Do the same on a jar already at its ceiling and you are over it, and “over the ceiling” is where beading, seeping and leaking start rather than where throw improves (more oil does not always mean stronger).

Three rules keep rounding harmless. Round the oil down and the wax up, never the other way. Round at the level of the melt, not the jar, so one decision covers the whole batch. And keep at least one percentage point of margin below the governing ceiling for anything that will be couriered in an Indian summer — margin absorbs the scale, the stir and the jar you filled slightly high.

The batch card: a formula you can repeat in November

Write eight things for every melt: date, wax grade and weight, oil name and weight, the load you computed from those two, add temperature, stir time, pour temperature, jar and fill weight. That is it. With those eight, any batch can be audited backwards — the load recomputed, a leak traced, a weak throw separated from a dosing error — and any batch can be scaled forwards without re-deriving anything.

Keep the card with the batch, not in a notebook that lives on the other table. Writing the wax grade matters more than makers expect: CSI 464 at 10% and Luxury Soy Wax Chunks at 10% are the same arithmetic against different ceilings — one is at its published maximum, the other is at its page’s recommended figure with three points of headroom. Six weeks later, “10% soy” will not tell you which candle you are holding.

From those eight fields everything else falls out without a second calculation: cost per candle for pricing, oil to reorder for the next run (how much a candle business needs), and the exact number to change when a test says the candle wants a point more or a point less.

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