Candle Wick Size Calculator
Determine the correct wick size for your candle from container diameter, wax type, and fragrance load.
Candle Wick Size Calculator
Calculator
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Formula: Effective Diameter = Container Diameter x Wax Factor x Fragrance Factor x Dye Factor x Shape Factor
Worked example — Recommended: CD-10, ECO-10, or HTP-104 | Single wick | ~16 hour burn time
Formula
Effective Diameter = Container Diameter x Wax Factor x Fragrance Factor x Dye Factor x Shape Factor
The effective diameter accounts for factors that influence heat requirements. Different wax types need more or less heat to achieve a full melt pool. Higher fragrance loads require slightly larger wicks. Dye can clog wicks, requiring upsizing. The effective diameter is then matched to wick manufacturer sizing charts.
Worked Examples
Example 1: 3-inch Soy Candle in Straight Jar
Problem:Determine wick size for a 3-inch diameter, 4-inch tall straight jar with soy wax, 8% fragrance load, no dye.
Solution:Base diameter: 3.0 inches Soy heat factor: 1.0 Fragrance factor: 1 + (8-6) x 0.02 = 1.04 Dye factor: 1.0 (no dye) Shape factor: 1.0 (straight) Effective diameter: 3.0 x 1.0 x 1.04 x 1.0 x 1.0 = 3.12 inches Recommendations: CD-10, ECO-10, HTP-104 Single wick | Burn time: ~16 hours Best series for soy: ECO or HTP
Result:Recommended: CD-10, ECO-10, or HTP-104 | Single wick | ~16 hour burn time
Example 2: 5-inch Coconut Wax Candle with Dye
Problem:Determine wick for a 5-inch wide, 3-inch tall jar candle using coconut wax, 10% fragrance, with dye.
Solution:Base diameter: 5.0 inches Coconut heat factor: 1.05 Fragrance factor: 1 + (10-6) x 0.02 = 1.08 Dye factor: 1.05 Shape factor: 1.02 (jar) Effective diameter: 5.0 x 1.05 x 1.08 x 1.05 x 1.02 = 6.09 inches Double wick needed (>4 inches) Each wick sized for ~2.5-3 inch diameter Recommendations: CD-7/10, ECO-6/10 per wick Burn time: ~12 hours
Result:Double wick: CD-7 to CD-10 each | ECO-6 to ECO-10 each | ~12 hour burn time
Frequently Asked Questions
How do I choose the right wick size for my candle?
Choosing the correct wick size is the most critical decision in candle making and depends on multiple factors working together. The container diameter is the primary determinant since the wick must produce enough heat to create a full melt pool from edge to edge. A wick too small causes tunneling where only the center melts, wasting wax. A wick too large creates excessive heat, potential sooting, and unsafe flame heights. Start by matching your container diameter to the wick manufacturer's guidelines, then adjust for wax type (soy needs more heat than paraffin), fragrance load (higher loads need slightly larger wicks), and additives like dye. Always make test candles with three sizes: the recommended size, one size up, and one size down, then burn-test each for 3-4 hours to evaluate performance.
What wick series works best for soy wax candles?
Soy wax candles generally perform best with cotton-core wicks from the ECO, HTP, or CD series. ECO wicks are a popular choice because they are made from cotton with a paper filament that promotes a consistent curl, creating a self-trimming effect that reduces carbon buildup and mushrooming. HTP wicks are designed specifically for vegetal and soy waxes, providing excellent melt pool performance and consistent flames. CD (Stabilo) wicks contain a series of interlocking cotton threads with a paper core, offering good rigidity and performance across many wax types including soy. Avoid zinc-core or lead-core wicks entirely. For 100% soy wax, most experienced chandlers start with ECO series wicks and adjust sizes through testing to achieve the ideal 1-inch melt pool per hour of burning.
What causes tunneling and how do I prevent it?
Tunneling occurs when only the wax around the wick melts, leaving a ring of unmelted wax around the container walls. The primary cause is using a wick that is too small for the container diameter, which does not generate sufficient heat to melt the wax from edge to edge. Candle memory also plays a role: the first burn establishes the melt pool pattern, so if the initial burn is cut short before the melt pool reaches the edges, subsequent burns will follow that same pattern. To prevent tunneling, use the correct wick size for your diameter, and always let the candle burn until the melt pool reaches completely to the container walls on the first burn (typically 1 hour per inch of diameter). If you have an already-tunneled candle, you can wrap the top with aluminum foil to redirect heat outward.
How do I know if my wick is too large or too small?
Several observable signs indicate wick sizing issues during a burn test. A wick that is too large will produce a flame taller than 1.5 inches, cause the container to become excessively hot (unsafe to touch), produce visible soot or black smoke, consume wax too quickly with a short burn time, and may cause the glass container to crack from excessive heat. A wick that is too small will produce a small, flickering flame under 0.5 inches, fail to create a full melt pool after 3-4 hours of burning, cause tunneling with a deep well forming around the wick, and may self-extinguish or drown in its own melt pool. The ideal wick produces a steady flame of 1-1.5 inches, achieves a full melt pool within 2-4 hours, shows minimal soot, and burns at approximately 4-5 hours per inch of candle height.
When should I use multiple wicks instead of one large wick?
Multiple wicks become necessary when a single wick cannot safely provide enough heat for a full melt pool. As a general rule, containers wider than 4 inches benefit from double wicks, and containers wider than 5.5 inches should use triple wicks. Using multiple smaller wicks instead of one large wick provides several advantages: more even heat distribution across the melt pool surface, reduced tunneling risk, lower individual flame heights for better safety, and more even fragrance throw. When using multiple wicks, space them evenly across the diameter and use wicks sized for half (double wick) or one-third (triple wick) of the container diameter. For example, a 5-inch container with double wicks should use wicks sized for 2.5-inch diameter candles. Test burns are especially critical with multiple wicks to ensure the combined heat is not excessive.
Why does a higher fragrance load push the recommended wick size up?
Fragrance oil is not fuel in the same way wax is; it changes the melt behaviour and viscosity of the melt pool and partially loads the wick's capillary structure, so the same wick draws and burns less efficiently. Candle Wick Size Calculator models that with a fragrance factor of 1 + (load - 6) x 0.02, taking six percent as the baseline. A 3 inch jar at 8 percent gives an effective diameter of 3.12 inches, while the same jar at 12 percent gives 3.36 inches, which is enough to move the recommendation up a size in most series.
What is wick mushrooming and does it mean my wick is wrong?
Mushrooming is the carbon ball that forms on the wick tip when more fuel is drawn up than the flame can fully combust. A small mushroom is normal, especially with fragrance oils and dyes; a large one that glows, sheds soot, or makes the flame dance is a signal the wick is oversized for the container. Series differ here: ECO wicks carry a filament that curls the tip into the hottest part of the flame so the carbon burns off, which is why they are recommended for soy. Trimming to a quarter inch before every burn removes the cap either way.
How does a wooden wick compare with a cotton wick of the same nominal size?
Wooden wicks burn as a thin flat flame along the width of the wick rather than a point flame, so they are specified by width and thickness rather than by a CD or ECO number, and cotton sizing charts do not transfer. They tend to need a wider profile than the equivalent cotton wick to reach the same melt pool, they are more sensitive to fragrance load, and they must be trimmed shorter, around an eighth of an inch, or they drown. Their appeal is the crackle and the wide even pool; the trade-off is a narrower margin between drowning and sooting.
What does the wick tab do and why should the wick be primed?
The tab, or sustainer, is the metal disc crimped to the base of the wick. It holds the wick centred and upright while the wax sets, and its neck height determines how much wax is left in the base when the flame reaches the bottom, which is the built-in safety cut-off that stops the glass overheating. Tabs come in a handful of stock diameters, and Candle Wick Size Calculator suggests a band from the container width, but confirm the exact tab and neck height against your wick supplier's listing rather than treating any one mapping as a standard. Priming means pre-coating the wick in wax so it lights readily and does not wick up raw fragrance on the first burn.
How should I structure a burn test to confirm the size?
Cure the candles fully first, then burn each in a draft-free spot in sessions of about four hours, recording the same measurements each time: melt pool depth, whether the pool reached the glass and after how long, flame height, any soot on the rim, and the container temperature by touch. A useful target is a pool that reaches full width without exceeding about half an inch deep, since a deeper pool means the wick is running hot. Repeat until the candle is spent, because problems often appear only in the last third when the flame sits close to the glass.
References
Background & Theory
Wick Series Comparison at a Glance
Wick manufacturers publish their own sizing charts, and the three series below are the ones this calculator's recommendation table draws from. They are not interchangeable one-for-one — a CD-10 and an ECO-10 are sized for similar containers but are built differently (paper-cored cotton braid vs. cotton/paper wrapped filament), so burn characteristics differ even at the "same" nominal size.
| Series | Construction | Best for | Typical range |
|---|---|---|---|
| CD (Stabilo) | Interlocking cotton threads, paper core | Paraffin, soy, blends — good rigidity in tapers and pillars too | CD-3 to CD-18+ |
| ECO | Cotton with paper filament, self-curling tip | 100% soy and natural waxes — reduces mushrooming/carbon buildup | ECO-1 to ECO-16 |
| HTP | Braided cotton engineered for vegetal waxes | Soy and soy blends needing a strong, consistent melt pool | HTP-62 to HTP-1512 |
Series characteristics per CandleScience's wick guide (see References). Always confirm the exact chart for your specific wick brand, since two suppliers can label similar constructions with different numbering.
Real-World Use Case: Sizing a New Wax Blend
Chandlers switching wax suppliers mid-production often keep their container and fragrance load the same but need to re-test wick size because the new wax's heat requirement differs. For example, moving from 100% soy (heat factor 1.0) to a coconut-soy blend (heat factor ~1.05) in the same 3-inch jar increases the effective diameter enough to bump a CD-10 recommendation up toward a CD-12 in this calculator's output — a small shift that is easy to miss without recalculating, but that shows up clearly as an "effective diameter" change here rather than requiring a fresh burn-test matrix from zero.
Reviewed for accuracy by Daniel Agrici, Founder & Lead Developer · Editorial policy
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