Jar fill and batch size.

Worked example

A 500 g batch with 10% left behind leaves 450 g to fill. A 4 oz jar is 4 x 28.349523125 = 113.40 g, so the batch fills 3 full jars with 109.81 g left over, just short of a fourth. In the other direction, 12 jars of 2 oz need 12 x 56.70 = 680.39 g in the jars, and with 10% left in the pot you should make 755.99 g.

How it works

Jar grams = size x 28.349523125 for ounces, the exact avoirdupois ounce. Usable grams = batch x (1 - loss / 100), full jars is usable divided by jar grams rounded down, and batch needed is jars x jar grams / (1 - loss / 100).

Use net weight, not the jar size on the label. A jar sold as 4 fl oz is a volume: a US fluid ounce is exactly 29.5735295625 mL, so a 4 fl oz jar holds 118.29 mL, but how many grams of lotion or butter that is depends on the product, so fill one and weigh it. This tool does not convert volume to weight for that reason.

Sources (opened 2026-10-08): Wikipedia, Ounce (international avoirdupois ounce exactly 28.349523125 g); Wikipedia, Fluid ounce (US fluid ounce exactly 29.5735295625 mL).

FAQ

How many 4 oz jars does a 500 g batch fill?

With 10% left in the pot, 450 g is usable and a 4 oz jar holds 113.40 g, so it fills 3 full jars with about 109.81 g left.

How much lotion do I need for 12 two-ounce jars?

The jars hold 680.39 g, and with 10% left in the pot you should make 755.99 g. Change the loss percent to match how much your own batches leave behind.

What is the difference between oz and fl oz on a jar?

Oz is weight and fl oz is volume. A US fl oz is exactly 29.5735295625 mL. How much a fl oz weighs depends on the product, so weigh a filled jar to find out.

How many grams is 1 oz?

Exactly 28.349523125 g for the international avoirdupois ounce.

How much product is left in the pot?

It depends on your tools and product. 10% is a common rule of thumb, not a published standard; weigh a batch before and after filling to find your own number.