Candle Wick Size Guide
Enter your jar diameter and wax type to get primary and secondary wick recommendations across all four major wick series - side by side. Adjusts for fragrance load automatically. Nothing uploaded.
Jar Settings
Wick Recommendations
| Series | Primary ? | Secondary ? | Diameter range |
|---|
Test protocol
- Burn for 1 hour per inch of jar diameter (minimum 2 hours).
- Melt pool should reach the jar edges within that time.
- Flame should be steady, 1-3cm tall, no black smoke.
- Mushrooming (carbon ball on wick tip) = wick too large - try primary next time.
- Tunnelling (melt pool doesn't reach edges) = wick too small - step up to secondary.
Wick Test Log
Learn more: wick sizing and candle testing
Why the wick is the part that goes wrong
Wax, dye and fragrance all announce themselves before the candle is ever lit. The wick only tells you what it thinks once the flame has been going for a couple of hours.
Undersize it and the candle tunnels, burning a narrow shaft down the middle and leaving a wall of wax stuck to the glass. Oversize it and you get a carbon ball on the tip, soot on the jar, and a flame taller than it should be. Both faults come from the same decision, which is why sizing gets tested rather than guessed.
How this guide picks a size
Each of the four series has its own list of size codes, and each code carries a jar diameter range. The guide finds the row your inner diameter falls into, then moves up or down that list by a fixed number of positions: one step for the wax you selected, another for the fragrance load. The Secondary column is always the next code above the primary in the same series.
Soy 464 at a fragrance load of 6% or less is the baseline, so those settings move nothing. The note under the jar diagram spells out which adjustments are active.
An offset can run past the end of a list, and when it does the recommendation stops at the last code. A 90mm jar in pure coconut wax at a 10% load asks for three steps up from CD-18 but there are only two left, so the CD row shows CD-22 with a dash for the secondary.
What the wax setting changes
Soy 464, soy C3 and coconut-soy blends all sit at zero offset, so switching between those three leaves every code where it was. Any difference between them shows up in burn testing rather than in the starting size.
Paraffin drops one size and beeswax drops two, on the basis that both run hotter than soy. Pure coconut goes the other way and gains a size because it burns cooler.
Stepping down has a floor. On a 45mm jar the smallest code in each series is already the answer, so beeswax and soy both land on CD-8 there and the wax setting appears to do nothing.
How fragrance load shifts the recommendation
Fragrance oil slows the burn, so a heavily scented candle needs more wick to keep the melt pool reaching the glass. Up to 6% the size is left alone, 6 to 10% moves it up one, and anything past 10% moves it up two.
The wax and fragrance offsets are added together before anything is looked up. A 75mm jar in soy at a low load gives CD-14 and ECO-6. The same jar in pure coconut at 8% adds a step for each, landing on CD-18 and ECO-10.
Reading the wick size chart
The diameter range in the last column belongs to the recommended code in the baseline soy chart, not to your jar. Once an offset has been applied that range sits above or below your actual measurement, which is expected rather than a mismatch.
All four series appear at once - CD, ECO, Cotton Core and Wood Wick - so you can cross-check against whatever is already in your supplies drawer. A CD wick size chart on its own only tells you the diameter range per code; it can't account for wax type or fragrance load the way this guide does. Most makers settle into one series and test within it. Wood wicks in particular behave differently enough that moving to them means restarting the testing.
Test protocol and melt pool rules
Burn for one hour per inch of jar diameter, with a two hour minimum. The melt pool should reach the glass within that window.
The flame should hold steady between 1 and 3cm with no black smoke. A carbon ball at the tip means the wick is too large, so drop back a code. A melt pool that never reaches the edge means it is too small, so move up to the secondary.
FAQ
What wick do I need for a 75mm soy jar?
With soy 464 and a fragrance load of 6% or less, a 75mm inner diameter gives CD-14 or ECO-6, with CD-16 and ECO-8 as the step up if it tunnels. Burn a test candle for about three hours and check that the melt pool reaches the glass before you pour a batch.
Why does paraffin get a smaller wick than soy?
The guide treats paraffin as burning hotter than soy and steps the recommendation down one size, and beeswax down two for the same reason. These are starting points for testing rather than fixed rules, so if the paraffin candle tunnels, move back up a code.
Why does the diameter range next to my wick not match my jar?
That range belongs to the wick code and comes from the baseline soy chart, so it only lines up with your jar when no adjustment applies. Choose paraffin or a high fragrance load and the code moves along the list while your jar stays the same width, so the two stop agreeing.