Candle Wax CalculatorCandle Wick Size Calculator: Match the Wick to the Jar
The wick is the engine of the candle. Too small and the candle tunnels; too big and it smokes, soots, and overheats the glass. Diameter is what decides.
This wick size calculator takes your container's diameter and wax type and returns the industry-standard wick size to start testing with — including when to double-wick.
Wick size calculator
Enter your container's diameter and wax type to get the recommended wick size for a clean, even burn.
How the wick lookup works
Wick sizing is not a formula — it is a lookup. Years of burn testing across the candle industry have produced standard pairings between container diameter and wick size, and this calculator applies them directly. Under 2 inches of diameter calls for a small wick (CD 6 / ECO 4); 2–3 inches takes a medium wick (CD 8 / ECO 8); 3–4 inches needs a large wick (CD 10–12 / ECO 10); anything over 4 inches is too wide for one wick, so the recommendation is two CD 8 wicks spaced evenly.
The wax type then adjusts the note. Soy and coconut burn cooler and slower, so they can need a wick size up from the table in wide containers; paraffin burns hotter and may need a size down. Gel wax needs zinc-core wicks rather than cotton, because the gel clings to plain cotton and starves the flame.
Limits: this is the industry starting point, not a guarantee. Always burn-test your exact wax, fragrance, and container combination before selling or gifting a candle.
The diameter-to-wick lookup table
The industry's standard starting points pair container diameter with wick size like this:
| Container diameter | Recommended wick | Why |
|---|---|---|
| Under 2 in | Small — CD 6 / ECO 4 | A narrow melt pool covers the whole surface |
| 2–3 in | Medium — CD 8 / ECO 8 | The most common candle size; the workhorse wick |
| 3–4 in | Large — CD 10–12 / ECO 10 | Needs a bigger flame to reach the walls |
| Over 4 in | Double wick — 2 × CD 8 | One wick cannot cover the surface safely |
CD and ECO are cotton wick series; the number is the size. Think of the table as the answer to 'where do I start testing' rather than the final word — your exact wax, fragrance, dye, and jar shape all nudge the ideal wick a little.
Wax-type adjustments: soy and coconut waxes melt and burn cooler, so in wide containers they may need one size up from the table to reach a full melt pool. Paraffin burns hotter and can often go one size down. Gel wax is the special case — it needs zinc-core wicks, because plain cotton wicks clog in gel and the flame starves.
Worked example: a 3-inch soy candle jar
Measure the inside of the jar at its widest point: 3 inches. The table puts 3 inches at the top of the medium band, so the starting wick is CD 8 / ECO 8 — but since it sits right on the boundary, a large (CD 10) is the smart alternate to test alongside it.
The wax is soy, which burns cooler than paraffin. That pushes toward the larger option: start the test with CD 10, keep a CD 8 candle as the comparison, and burn both.
After a 3-hour burn, check the melt pool. The winner is the wick that melts wax all the way to the glass within 2–3 hours, holds a steady flame about an inch tall, and leaves no smoke marks on the jar. If both pass, pick the smaller one — it is safer and the candle burns longer.
Limitations of wick charts
No chart knows your exact candle. Fragrance load, fragrance type, dye amount, container shape (a flared tumbler burns differently from a straight jar), and even wick batch variation all move the ideal size. The lookup gets you to the right neighborhood; only a burn test of the finished candle confirms the address.
Double-wicking deserves extra care: two wicks interact, and poor spacing creates hot spots. Keep them evenly spaced and centered, and test the finished candle the same way you would a single-wick one.
Finally, never reuse a chart result across a recipe change. Switching waxes, changing fragrance load, or moving to a different jar means re-testing from the table's starting point.
Related calculators
- Soy Wax CalculatorFree soy wax calculator: enter container diameter, height, and candle count to get exact wax and fragrance oil amounts in grams, with a worked example.
- Paraffin Wax CalculatorFree paraffin wax calculator: batch wax weight, 15% second-pour reserve for shrinkage, and fragrance oil at 8–12% load.
- Gel Wax CalculatorFree gel wax calculator: batch gel wax weight and safe 3–5% fragrance loads.
Start from the candle wax calculator to find a different tool.
Frequently asked questions
What do wick names like CD 8 and ECO 8 mean?
They name the wick series (CD and ECO are the two most common cotton wick families) and the size number, which roughly tracks the wick's thickness. A higher number means a bigger flame and a wider melt pool. CD 8 and ECO 8 are comparable sizes from different series.
What happens if my wick is too small?
The flame cannot melt wax all the way to the container walls, so the candle tunnels — a narrow hole burns down the middle while a ring of unmelted wax stays stuck to the glass. The candle looks bad, wastes wax, and the flame can drown in its own melt pool.
What happens if my wick is too big?
An oversized wick makes a tall, smoky flame, overheats the container, and grows a mushroom-shaped carbon cap that drops soot. In the worst case it can crack the glass from excess heat. If your candle smokes or the flame dances wildly, size down.
When should I use two wicks instead of one?
When the container is wider than about 4 inches. No single wick can melt a pool that wide without becoming dangerously large itself. Space the two wicks evenly — roughly at the one-third and two-thirds marks across the diameter.
Does the fragrance I add change the wick size?
It can. Heavy fragrance loads and certain fragrance oils burn differently enough to shift the ideal wick a size up or down. That is why burn-testing uses the finished, fragranced candle — never test with plain wax and assume the result carries over.
Can I just guess and skip burn testing?
For your own use, the table recommendation is usually fine. For anything you sell or gift, test: burn the candle 3–4 hours at a time, check that the melt pool reaches the edge within 2–3 hours, and confirm the flame stays steady with no smoking or mushrooming across the whole candle.
Found an error? Report it