Choose by Diameter, Then Test
Wick makers size wicks mainly by container diameter, not height or volume. A wider jar has a bigger surface of wax to melt, so it needs a bigger wick or more than one. The wick series (CD, ECO, HTP and others) and the number within it vary by manufacturer, and your wax, oil and dye change the result. The chart below is a starting point for test burns, not a final answer.
Starting-Point Chart (Soy Wax, Single Wick)
This is the same chart shown on the MakersMath Candle Wick Calculator page. We have not checked it against a wick manufacturer's published chart, so verify against your supplier's chart before buying wicks in bulk.
| Container diameter | CD | ECO | HTP | Melt-pool surface area (sq in) | |---|---|---|---|---| | 1.5-2 in | CD 4-6 | ECO 2-4 | HTP 52-62 | 1.77-3.14 | | 2-2.5 in | CD 6-8 | ECO 4-6 | HTP 62-73 | 3.14-4.91 | | 2.5-3 in | CD 8-10 | ECO 6-8 | HTP 73-83 | 4.91-7.07 | | 3-3.5 in | CD 10-14 | ECO 8-12 | HTP 83-93 | 7.07-9.62 | | 3.5-4 in | CD 16-18 | ECO 12-14 | HTP 104-105 | 9.62-12.57 | | 4 in and wider | Double or triple wick | | | 12.57 and up |
Surface area is pi x radius x radius at the edge diameters; a 3 in container has pi x 1.5 x 1.5 = 7.07 sq in. It shows how much wax one wick has to melt. A 4 in container has about 78% more surface than a 3 in one (12.57 / 7.07).
Wax Type Changes the Wick
The same jar can need a different wick depending on the wax, whether soy, paraffin, coconut blend or beeswax. Do not rely on a single rule of thumb for which way to adjust. Check your wax supplier's wick chart for your exact wax and use that.
Small Containers (Under 3 Inches)
Small jars still need enough wick to melt wax out to the edges, so do not assume the smallest wick is best. For a 2 in container, use the 1.5-2 in or 2-2.5 in row as your starting point and test one size either side. Votives sitting in holders follow the same logic.
Medium Containers (3 to 4 Inches)
This is the range most hobby makers use. Start at the row for your diameter and test the sizes on either side. In the 3-3.5 in row the range runs from CD 10 to CD 14 (ECO 8-12), so there is real room to move up or down depending on your wax and oil.
CD vs ECO
CD and ECO are different wick constructions. Their burn characteristics depend on your wax, so read the supplier's description for the series you buy instead of assuming one is hotter or cooler.
Large Containers (Over 4 Inches)
A single wick has to melt a wide surface, so the chart moves to multiple wicks at 4 in and over. Treat each wick as covering its own 2 to 2.5 in zone, space them evenly, and test for hot spots.
For example, a 4.5 in container has 15.90 sq in of surface (pi x 2.25 x 2.25). Confirm multi-wick sizing with your supplier's guidance.
Square, Rectangular and Oval Containers
These do not follow the round-container chart exactly, because the corners are farther from the flame. Start from the chart for the narrowest width, treat long containers as several zones, and test. Your supplier's chart may give specific guidance for these shapes.
Testing a Wick: One Hour per Inch
The test is the melt pool, not the clock on the box:
- Make test candles in the same container with three wick sizes from the chart row: the middle one and one size either side.
- Use the exact same wax, oil load, dye and pour temperature in all three.
- Light each one and watch for a full melt pool reaching the container walls within about one hour per inch of diameter (about 3 hours for a 3 in jar).
- Keep burning for at least 4 hours total, never leaving a candle unattended.
- Note flame height, smoking, soot, and how hot the container gets.
Reading the Results
- Tunneling (wax left on the walls while the center burns down): the wick is probably too small.
- Large flame, soot, smoke, or a very hot container: the wick is probably too large.
- Mushrooming (a carbon ball on the wick tip): often a sign of an oversize wick, but fragrance oil and dye can also cause it. Trim the wick before each burn, and if it persists, try the next size down.
- Heavy fragrance load: the site's wick calculator warns that loads above 10% can clog wicks, so test at your intended load, not an assumed one.
Wick Notes for Fragrance Load
Change the fragrance load and you may change the best wick. Test at the final load. For choosing the load itself, see the fragrance load guide.
Key Takeaways
- Choose by container diameter first; height matters less
- The chart above is a starting point, unverified against a maker's chart
- Check your supplier's chart for your exact wax
- Test three sizes; look for a full melt pool in about one hour per inch of diameter
- From 4 in wide, plan on multiple wicks
- Keep a log of container, wax, load, wick and result
Ready to run your own numbers? Try our free Candle Wick Calculator and Candle Wax Calculator.