I Want to Standardise One Wick Across Multiple Candle Jars — How Similar Do Their Internal Diameters Need to Be?
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I Want to Standardise One Wick Across Multiple Candle Jars — How Similar Do Their Internal Diameters Need to Be?
Why can't small differences be ignored? Melt-pool area grows with the square of the diameter. A 5 mm wider inside gives about 14.8% more pool at 7 cm and about 19.0% more at 5.5 cm, so the same gap matters more in small jars.
Can I group jars from the listings? Only on paper. No CSI listing states an inside diameter; "7 cm" appears as width, outer rim and plain diameter on three different jars. Measure three of each jar inside, at pool height, before you draw a single band.
What does proving a band cost? In our worked example, five candles across three 7 cm listings use ₹917.97 of wax, oil and wicks, against ₹2,985.49 of wax and oil alone for a full three-wick bracket on every jar.
- Straight answer: how similar is similar enough?
- Why there is no universal millimetre tolerance
- Grouping CSI jars on paper: what the listings allow
- Measure the spread inside one jar type first
- The edge-jar method: prove a band with two jars
- Pass, fail and what else must match
- Worked example: one wick for the 7 cm group, costed
- What to buy to prove a band
- Keeping a proven band honest
- Frequently asked questions
Why there is no universal millimetre tolerance
You will find confident figures online for how far jar diameters can differ before a wick stops working. We are not going to add one, for three reasons you can check yourself.
1. The pool grows with the square of the diameter
A wick has to melt a circle of wax, and the area of a circle is π × r² using the inside radius. Area does not rise in step with diameter; it rises with its square. Going from 6.3 cm to 7.0 cm inside is an 11% wider jar and 23.5% more wax surface. Worse, the same gap in millimetres means more in a small jar than a large one, which kills any single mm rule before it starts:
| Narrower jar, inside | +2 mm | +3 mm | +5 mm | +10 mm |
|---|---|---|---|---|
| 5.5 cm | 7.4% | 11.2% | 19.0% | 39.7% |
| 6.3 cm | 6.4% | 9.8% | 16.5% | 34.3% |
| 7.0 cm | 5.8% | 8.8% | 14.8% | 30.6% |
| 9.3 cm | 4.3% | 6.6% | 11.0% | 22.7% |
Read across the +5 mm column: 19.0% more pool in a small jar, 11.0% in a large one. A "5 mm tolerance" would be generous for your smallest jars and fussy for your largest. The worked maths for a single 5 mm step is in the 5 mm difference post.
2. The wick's window depends on the rest of your formula
How wide a pool one wick can hold depends on wax, fragrance oil and load as well as the wick. A wick that reaches the glass in a 6.8 cm jar with one oil may stop short with another; that is why different fragrance oils can need different wicks in the same jar. So even a proven band is proven for one formula. Change the oil or the load and the band's edges can move.
3. Diameter is not the only thing that has to match
Two jars can share an inside diameter and still burn differently: a 10 cm-tall jar keeps the flame deeper for longer than an 8 cm one, a jar that narrows towards the bottom shrinks the pool late in the burn, and a thick base shortens the burn column. Diameter bands group jars that might share a wick. Shape and depth decide whether they do.
Grouping CSI jars on paper: what the listings allow
Of CSI's 72 container listings, 21 state some diameter (outer, base or unspecified) and 20 give only a width; none states an inside diameter. The table covers every in-stock glass jar listing with a usable figure, sister colours grouped, quoted as written, with the paper group it falls into. Heights matter as much as widths here, so they are included.
| Listing | Figure as written | Height | Stated fill | Paper group | What is open |
|---|---|---|---|---|---|
| Heart Cutout Velvet Candle Jar 50 g (Red) | "5.3 cm in diameter" | 4.3 cm | "up to 50 grams of wax" | on its own | Inside or outside; Red in stock, White out of stock |
| Shiny Glass Jar with lid, 120 g (Black, Amber, Pink; Red, Green, Navy Blue, Purple) | "6 cm diameter" | 6.5 cm | "Capacity: 120 gm" | listed 6 cm | Inside or outside; the Amber page's text describes the Black jar |
| Shot Glass Jar 130 g | "Diameter - 6cm" | 8 cm | 130 g | listed 6 cm | Inside or outside; pack count (six or five) |
| Matte / Frosted / Glossy 200 ml family | "width 7 cm" | 8 cm | "fill weight of 200 ml" | listed 7 cm | "Width" is not a diameter type; ml not g |
| Clear Glass Jar with Golden Lid (150 gram) and coloured 150 g sisters (Amber out of stock) | outer rim 7 cm, base 6.5 cm | 8 cm (sisters: with lid) | 150 g | listed 7 cm | Page calls it both "curved" and "straight-sided" |
| Green Iridescent Jar with Bamboo Lid 300 g | "Diameter - 7cm" | 10 cm | 300 g | listed 7 cm | Inside or outside; nothing about walls |
| Apothecary Glass Candle Jar with Dome Lid (500 g, 700 g) | outer rim 10 cm, base 10 cm | 10.8 cm | ~500 to 700 g | listed 10 to 11 cm | One set of figures for two sizes; "curved silhouette" |
| Premium Glass Clip Top Container | "11cm * 11cm * 10cm" | one of those | 550 g | listed 10 to 11 cm | Which figure is the diameter; shape |
Three things stand out. The 7 cm group is written three different ways (width, outer rim, plain diameter), and nothing tells you whether the three mean the same measurement. Inside each group the heights differ: 6.5 and 8 cm in the 6 cm group, 8 and 10 cm in the 7 cm group. And the gap between groups is large: if the 6 and 7 cm figures are both outside measurements with similar walls, the 7 cm jars carry about 41.3% more pool than the 6 cm ones. Across that gap, sharing a wick would be a surprise; inside a group it is a question worth testing. Whether an outside figure can stand in for an inside one is taken apart in The Supplier Gives the External Diameter of the Candle Jar — Can I Use That for Wick Selection or Do I Need the Internal Diameter?.
Measure the spread inside one jar type first
Mass-produced glass varies from piece to piece and batch to batch. Before you ask whether the 200 ml Matte and the 300 g Iridescent can share a wick, find out how much three Matte jars differ from each other. That spread is the floor: if your own Matte jars differ by 2 mm inside, no band built on them can pretend to be tighter.
How to measure the inside diameter
Use callipers with inside jaws if you have them; otherwise lay a steel ruler across the mouth and read the inside edges, or cut a strip of card to fit snugly across the inside and measure the strip. Measure at three heights: just below your fill line, where the first pools form; half-way down; and about 1 cm above the inside floor, near where you will stop the burn. Turn the jar 90 degrees and repeat, because a jar can be slightly oval. If you only have the outside figure, measure the wall at the rim and take off two wall thicknesses; the full method is in the diameter-and-wick hub.
| Record | Where | Why it matters for a shared wick |
|---|---|---|
| Inside diameter, top | about 1 cm below the fill line, two directions | Sets the first-burn pool the wick must reach |
| Inside diameter, middle | half-way down the wax | Shows a taper or bulge |
| Inside diameter, bottom | about 1 cm above the inside floor | Shows whether the pool shrinks late in the burn |
| Inside depth | rim to inside floor, with a skewer | Tall jars keep the flame deep for longer |
| Fill line | cm below the rim | Must be the same across the band |
| Spread within the type | largest minus smallest of three jars | The floor for any band that includes this jar |
The edge-jar method: prove a band with two jars
A wick that works in the narrowest jar of a band and in the widest has shown it can cope with both ends. The jars between are only covered if they sit between the edges on everything else that matters: depth, shape and fill line. That is the whole idea; the steps make it repeatable.
Pass, fail and what else must match
| Check | Narrow edge passes if… | Wide edge passes if… | Typical failure |
|---|---|---|---|
| Pool width, first burn | reaches the glass without rushing ahead of the flame's control | reaches the glass within about 3 to 4 hours | Wide: a ring of solid wax at the glass |
| Pool depth | stays roughly 0.5 to 1 cm | not shallow and waxy at the edge | Narrow: a deep pool and a big flame |
| Flame | steady, no tall flickering or smoke | not shrinking or drowning | Narrow: tall flame, soot on the glass |
| Final third | glass not too hot to handle, flame clear of the glass | still pools as the flame goes deeper | Deep jars: flame shrinks low down |
| Wick behaviour | little mushrooming after a 4-hour burn | stays upright and lit | Either: drifting wick, one side hotter |
Soot, heat and flame size are the narrow-edge signals; tunnelling and a wax ring are the wide-edge signals. If one wick shows both across a band (hot in the narrow jar, rings in the wide one), the band is too wide for that wick, and no single wick will close it.
What else has to be identical across a band
A band is a promise that the wick sees the same job in every jar. That holds only if these match: wax (switching from CSI 464 to a coconut-soy blend is a new test), fragrance oil and load (a band proved at 8% of one oil is not proved at 10% of another), fill line (a jar filled closer to the rim burns at a different height relative to the rim), shape class (straight-sided with straight-sided), and depth within the range your edges covered. Colour, frosting and label do not change the wick; the glass under them can, so measure one jar of every colour you sell. If your jar narrows towards the bottom, the diameter to band on is its own question, answered in My Jar Narrows Toward the Bottom — Should I Select the Wick Based on the Top, Middle or Bottom Internal Diameter?.
Worked example: one wick for the 7 cm group, costed
Suppose you sell in the Matte 200 ml ("width 7 cm", 8 cm tall), the Clear 150 g (outer rim 7 cm, base 6.5 cm, 8 cm tall) and the Green Iridescent 300 g ("Diameter 7cm", 10 cm tall), and C2 already works in the Matte. For costing only, suppose your measurements put the Clear 150 g narrowest at pool height and the Iridescent widest (it is also the deepest, so it would be an edge anyway). Your jars may sort differently; measure before you pour.
| Candle | Jar | Candle weight | Oil at 8% | Wax | Wick |
|---|---|---|---|---|---|
| 2 × narrow edge | Clear 150 g (₹94.40 each) | 150 g (listing figure) | 12 g each | 138 g each | C2 |
| 2 × wide and deep edge | Green Iridescent 300 g (₹150.00 each) | 300 g (listing figure) | 24 g each | 276 g each | C2 |
| 1 × middle spot check | Matte 200 ml (₹70.80) | 150 g (planning figure) | 12 g | 138 g | C2 |
| Total | ₹559.60 of jars | 1,050 g | 84 g: ₹380.62 | 966 g: ₹490.15 | 5 × C2: ₹47.20 |
The fill weights are the listings' own figures and the 150 g planning figure from the 200 ml fill-weight hub; weigh your own test pours. The oil is Woody Oud Fragrance Oil as a costing example only: its page states "candles (6-10%)", and at 100 g and above it is flat at ₹4.53 per gram, so the 100 g bottle is the sensible test size. Wax is Luxury Soy Wax CSI 464 (page: up to 10%, so 8% sits inside it) at ₹0.51 per gram.
What to buy, and what is left over
Materials: CSI 464 1 kg (₹507.40) plus 500 g (₹260.00), because 966 g of wax leaves too little in a single 1 kg bag for pitcher loss and top-ups; 100 g of Woody Oud (₹453.12); C1, C2 and Cotton Braided packs of 10 (₹59.00, ₹94.40, ₹120.00). Total ₹1,493.92. If you own none of the jars, add a Matte pack of 5, two Iridescent jars and a Clear 150 g pack of 10 (₹1,598.00), for ₹3,091.92 in all; eight Clear jars and four Matte jars remain for measuring or production.
Watch the oil. The five candles use 84 g of a 100 g bottle, leaving 16 g. If the wide edge fails and you retest two Iridescent candles on Cotton Braided, they need 48 g of oil (₹217.50) and 552 g of wax (₹280.08), a little more than the 534 g left from 1.5 kg. Neither the bottle nor the bag covers the retest, and it needs two more Iridescent jars (₹300.00), so buy a second 100 g of oil then, or a 500 g if the band is likely to become production (at ₹4.53 per gram it is no cheaper per gram, only fewer orders).
Why the edges, not everything
The alternative is a full bracket on every jar: three wick rungs, two candles each, three jar types, eighteen candles and 3,600 g of candle. That is ₹1,680.51 of wax and ₹1,304.99 of oil, ₹2,985.49 together, against ₹870.77 for the band test: ₹2,114.73 less in wax and oil. It also takes more than three times the candle-burn hours. A full bracket is still the right move for a jar with no working wick at all. For a band where one jar already works, test the edges.
| Result | Band decision | Wicks you stock | Next test |
|---|---|---|---|
| Both edges pass, middle spot check passes | One band: all three jars on C2 | C2 | Final-third check on one more Iridescent before launch |
| Iridescent leaves a wax ring on C2 | Split: Matte and Clear on C2; Iridescent tested alone | C2 + whichever rung passes in the Iridescent | Two Iridescent candles on Cotton Braided (more oil needed) |
| Clear 150 g runs hot and sooty on C2 | Split: Clear tested on C1; Matte and Iridescent stay on C2 if the Iridescent passed | C1 + C2 | Two Clear candles on C1 |
What to buy to prove a band
Wicks first, because they are the variable; then jars from the two paper groups most likely to be merged. Chosen on what the pages state, price and stock on 26 September 2026, not on burn performance: CSI publishes no burn data for any jar and wick pairing.
| Pack | Price | Per wick | What it covers |
|---|---|---|---|
| Thin (C1) / 10 Wicks | ₹59.00 | ₹5.90 | the rung below the candidate, for the narrow edge |
| Thin (C1) / 100 Wicks | ₹590.00 | ₹5.90 | a production band that proved on C1 |
| Thick (C2) / 10 Wicks | ₹94.40 | ₹9.44 | five band-test candles plus five spares |
| Thick (C2) / 100 Wicks | ₹944.00 | ₹9.44 | a production band that proved on C2 |
| Pack | Price | Per wick | What it covers |
|---|---|---|---|
| Pack of 10 | ₹120.00 | ₹12.00 | the rung above the candidate, for the wide edge |
| Pack of 50 | ₹600.00 | ₹12.00 | same per wick as the 10-pack |
| Pack of 100 | ₹1,200.00 | ₹12.00 | a production band that needs it |
| Pack | Price | Per jar | What it covers |
|---|---|---|---|
| Pack of 5 | ₹354.00 | ₹70.80 | one middle-SKU spot check plus four jars to measure |
| Pack of 10 | ₹708.00 | ₹70.80 | no saving over two packs of 5 |
| Pack | Price | Per jar | What it covers |
|---|---|---|---|
| Single jar | ₹150.00 | ₹150.00 | buy two: the tallest 7 cm listing, and a likely edge jar |
| Pack | Price | Per jar | What it covers |
|---|---|---|---|
| Pack of 6 | ₹288.00 | ₹48.00 | measure all six, burn two as the 6 cm group edge |
Keeping a proven band honest
A band proved once is proved for that batch of glass, that oil and that load, so write down which. Record each band on one sheet: the jar types in it, their measured inside diameters at three heights, the spread within each type, the edge jars, the wick, wax, oil and load, and the burn logs. It is short, and it is what you check against when something changes.
| Change | Retest |
|---|---|
| New jar batch, inside diameters within the recorded spread | Measure three; no burn needed |
| New jar batch, a jar outside the band's edges | Burn that jar as a new edge (sorting jars that arrive different) |
| New jar type added to the band | Measure; if it becomes an edge, burn it; if it sits between, one spot check |
| New oil or higher load | Wide edge at least; narrow edge if the oil is known to burn hot |
| New wax | Both edges; treat it as a new band |
| Same-looking jar from a new supplier | Measure against the sheet (what must match when switching suppliers) |
If a new, wider jar arrives for a band that was proved on 7 cm glass, the question is no longer "does the band stretch" but "does this jar need its own wick"; the retest scope for a 7 cm to 8 cm move is in I Already Finalised My Wick for a 7 cm Jar — If My New Jar Is 8 cm Wide, Do I Have to Repeat the Entire Burn-Testing Process?.
CandleMakingSuppliesIndia sells the jars and wicks named here and does not sell finished candles. This page tells you that no CSI listing states an inside diameter, that our "7 cm" is written three ways on three jars, and that the test may leave you stocking two wicks rather than one. We would rather you proved a band than bought a hundred wicks on our word.
Every price and per-jar figure was verified on CSI's live store on 26 September 2026; every pack in a pick table was in stock on that date, and out-of-stock colours and listings are named as such. Dimensions and wick wording are quoted from the product pages; where a page is silent, we say so.
The pool-area percentages are geometry. The 0.35 cm wall, the edge-jar method, the retest table and the outcome that the Clear 150 g is narrowest are our judgement and illustrative assumptions; the 3 to 4 hour full pool, 0.5 to 1 cm pool depth and 1 cm stop-line are candle-maker rules of thumb. For bulk pricing, GST invoicing, and MSDS and IFRA documentation on request, message us on WhatsApp at +91 7397976926.
Frequently asked questions
- My Candle Jar Holds 200 ml but Has a 7 cm Internal Diameter — Which Measurement Should I Use When Choosing the Wick?
- The Supplier Gives the External Diameter of the Candle Jar — Can I Use That for Wick Selection or Do I Need the Internal Diameter?
- How Much Can a 5 mm Difference in Candle Jar Diameter Affect the Wick Size and Melt Pool?
- I Want to Reduce the Number of Wick Sizes in My Business — Should I Choose Candle Jars With Similar Diameters Even If Their Capacities Differ?
- My Jar Narrows Toward the Bottom — Should I Select the Wick Based on the Top, Middle or Bottom Internal Diameter?
- I Have a Straight-Sided 3-Inch Candle Jar — How Do I Choose the First Three Wick Sizes to Test Rather Than Guessing Randomly?
- I Already Finalised My Wick for a 7 cm Jar — If My New Jar Is 8 cm Wide, Do I Have to Repeat the Entire Burn-Testing Process?
- I'm Switching Candle Jar Suppliers but the New Jar Looks Almost Identical — What Measurements Must Match Before I Keep the Same Wick?
- My Glass Jars Are Cheap but Their Dimensions Vary Slightly Between Batches — How Can That Affect Wick Testing and Production Consistency?
- I Received 500 Candle Jars and Some Have Different Internal Diameters — Should I Reject Them If My Wick Was Tested on a Specific Diameter?
Customer reviews: The six reviews at the top of this page are genuine, published Judge.me reviews left by CSI customers on the product pages named on each card — Clear Glass Jar with Golden Lid (150 gram), Eco Candle Wicks, White Matte Glass Jar, Woody Oud Fragrance Oil. They are general product reviews, not assessments of the container advice on this page. Names, star ratings, dates and products are as recorded by Judge.me and wording is unedited. "Verified buyer" appears only on reviews Judge.me recorded as verified — Monika Deep, Subhankar Roy, Soumili Gope, Renam Dhoundiyal. The reviews from Ashwini, Ashwini are published but not recorded as verified, and carry no badge. Reviews below five stars are included as published, not filtered out.
Figures verified 26 September 2026, CSI live pricing: Eco Candle Wicks Thin (C1) 10 ₹59.00, 100 ₹590.00; Thick (C2) 10 ₹94.40, 100 ₹944.00; Cotton Braided Wicks Ready Made 10 ₹120.00, 50 ₹600.00, 100 ₹1,200.00; White Matte Glass Jar and in-stock 8 × 7 cm sisters, pack of 5 ₹354.00, pack of 10 ₹708.00 (Pink Matte, Frosted Brown and Orange Frosted out of stock); Clear Glass Jar with Golden Lid (150 gram) pack of 10 ₹944.00, pack of 20 ₹1,888.00; Green Iridescent Jar with Bamboo Lid 300 g ₹150.00 (White Iridescent out of stock); Shot Glass Jar 130 g pack ₹288.00; Black Shiny Glass Jar with Golden Lid pack of 1 ₹47.20, pack of 5 ₹236.00 (₹47.20 each); Luxury Soy Wax CSI 464 500 g ₹260.00 (₹0.52/g), 1 kg ₹507.40 (₹0.51/g), 5 kg ₹2,537.00 (₹0.51/g), 10 kg ₹5,074.00 (₹0.51/g); Woody Oud Fragrance Oil 15 g ₹93.22 (₹6.21/g), 50 g ₹271.40 (₹5.43/g), 100 g ₹453.12, 500 g ₹2,265.60, 1 kg ₹4,531.20 (₹4.53/g). Per jar or per wick = pack price ÷ units; per gram = price ÷ grams, two decimals.
Non-price figures: pool area = π × r² on the inside radius; percentages are geometry, not burn results. The 0.35 cm wall is an illustrative assumption, not a listing figure. Fill weights in the worked example are the listings' stated figures (150 g, 300 g) and the series' 150 g planning figure for the 200 ml jar; load is 8% of total candle weight. The 3 to 4 hour full pool, 0.5 to 1 cm pool depth, one hour per 2.5 cm and 1 cm stop-line are rules of thumb. The measuring outcome in the worked example is hypothetical, for costing. Dates are calendar facts. Costs exclude labour, freight, packaging and GST.