Jar Fill Weight Calculator: Grams, Density and Headspace
Enter the fill weight in grams and the product density; the calculator returns the smallest stock jar that holds it with headspace.
Designed by Joe Joo · 8PCK, Shantou
Wax, cream and scrub are sold by weight but bought by volume — and the headspace the filler leaves is the part everyone gets wrong.
Want a Person to Check It?
Send the numbers and we reply with a written quotation, lead time and a sample plan — usually within a few hours, Mon–Sat.
The Formula, the Assumptions, and Where It Stops
- Convert grams to millilitres: ml = grams ÷ density.
- Add the headspace the filler leaves: needed = ml ÷ (1 − headspace).
- Take the smallest stock size above that number — an under-filled jar reads short on shelf.
Assumptions. Density is approximate (water 1.00, lotion 0.95, oil 0.90, wax 0.86, salt scrub 1.30). Headspace is the filler's own requirement, usually 5–12 %.
Standards we work to. ISO 9001:2015 (quality system, cert PCC85724Q01277R1S) · EU 10/2011 (plastic food-contact, migration report E2032) · RoHS (PE B-R01612E2033, PET B-R201133464) · ISO 4180 (packaging for transport). The calculator is a planning tool: the approved drawing and the migration report decide the final specification.
Where it does not apply. It sizes a container; it does not set the fill line. The filler's validation wins.
Send the Numbers, Get a Person
Reply with the result above and we come back with a written quotation, packing data and a sample plan — within one business day.
Worked examples
Grams to millilitres, then to the nearest stock jar. The headspace number is the one buyers usually forget.
| Input | Product volume | With headspace | Stock size |
|---|---|---|---|
| 250 g cream, density 1.0, 8 % headspace | 250 ml | 272 ml | 300 ml |
| 200 g gel, density 0.95, 10 % headspace | 211 ml | 234 ml | 240 ml |
| 500 g lotion, density 1.02, 6 % headspace | 490 ml | 521 ml | 750 ml |
Why Headspace Matters More Than the Label Weight
A jar labelled 240 ml holds 240 ml of product plus the air the filler leaves. With wax at 12 % headspace a 250 g pour needs a 300 ml jar, not a 240 ml one — which is why fill weight is not the same as capacity.
How to Read the Result
The number is the smallest stock size that holds the pour with headspace. If it falls between two sizes, take the larger one: an under-filled jar looks short on shelf and over-filled wax spills in transit.
Questions About This Tool
Is this a filling specification?
No — it is a sizing check. The filler's own headspace requirement wins.
What density should I use?
Approximate: water 1.00, lotion 0.95, oil 0.90, candle wax 0.86, salt scrub 1.30.
Can you make a custom size?
Yes, a new mould is about USD 850 and 15–20 days.
Didn't Solve It?
Tell us what you are trying to pack and we will tell you what fits, what it costs and how long it takes. No forms if you would rather just message.