Free calculator
Bottle batch calculator
Bottles are sold by volume and perfume is made by weight, so there is a conversion in the middle of this that people either skip or guess at. This does it properly.
The sum, in words
Bottles are sold by volume and perfume is made by weight, so there is a conversion in the middle and it is the step people skip.
Multiply the number of bottles by what each one holds to get the total volume. Multiply that by the density of the finished liquid to get the total weight. Take the strength percentage of that weight, and that is your concentrate; whatever is left is the alcohol and anything else in the base.
Fifty bottles of 50 ml is 2,500 ml. At a density of 0.87 that is 2,175 g of finished liquid. At 20 percent, that is 435 g of concentrate and 1,740 g of everything else.
Why the density matters, and where to get it
Alcoholic perfume is lighter than water. A finished eau de parfum typically lands somewhere around 0.85 to 0.90 grams per milliliter, depending on the alcohol, the water content and how heavy the concentrate is. Use 1.0 and your batch is roughly 15 percent short, which is seven or eight bottles missing from a run of fifty.
The default here is a reasonable figure for an alcoholic perfume, and it is not your figure. Measure it once on your own base: weigh a known volume at a known temperature and divide. It takes two minutes, it is the same for every batch you make on that base, and it turns an estimate into a number.
Always make more than you need
A batch that comes out to exactly the last bottle leaves you one short, every time. Liquid stays in the mixing vessel, in the filter, in the tubing and in the filling head, and a little is lost to every transfer.
Five to ten percent over is normal, and more than that on a first run of an unfamiliar setup. It is cheaper than a second batch, and a second batch is not the same batch: it gets its own number and its own record, and now you have two lots of a product you meant to have one of.
The strength decides more than the smell
Before you fill anything, be sure the strength is the one the compliance work was done at. Every IFRA limit and every allergen threshold is a percentage of the finished product, so a batch bottled at 25 percent when the assessment was done at 20 is a batch whose figures are all a quarter higher than the ones on file.
It also decides the label. The allergen declaration is a consequence of the formula and the strength together, so labels printed for one strength are not valid for another.
What this calculator does not do
It works out what to weigh. It does not record what you actually weighed, which is the number that matters afterwards: what came off the balance rather than what was planned, and the strength that truly resulted rather than the one intended. That is the batch record, and it is what a question about one bottle three years from now is answered from.