Jar diameter

A starting chart by container width, not wishful thinking.

Jar diameter is the quickest way to narrow a wick test, but it only works if you use the inside width and keep wax type, fragrance load, and cure time in the notes beside it.

Jar diameter	Typical starting move	What to watch
Up to 2.25 in	Start with a smaller wick and test for full melt pool by hour three.	Tunneling if the wick is too timid.
2.5 to 3 in	Most container candles live here. Start near the middle of your wick family chart.	Heat and soot balance matters most here.
3.25 in and above	Expect more testing, double-wick decisions, or stronger wick families.	Uneven melt pool and stubborn side wax.

Measure the part that matters

Use the inside width where the wax actually sits. Decorative outer glass, thick walls, and rounded shoulders can all make the label size feel larger than the real burn area.

Measure across the inside, not the outer rim.
Recheck if the jar narrows at the top.
Write the measurement on the printable sheet before the pour.

When width stops being enough

Past about 3 inches, jar diameter alone stops answering the question. That is where double-wick tests, thicker wax, or a different container shape start changing the outcome more than one wick step.

Wide soy jars can need paired small wicks instead of one aggressive wick.
Dense beeswax jars can still underperform with a flame that looks healthy.
Heavy fragrance load can mimic a width problem when it is really a performance problem.