Also known as: Take-up Ratio, Flute Take-up Factor, Corrugation Factor
The take-up factor is the length of fluting medium consumed per unit length of corrugated board, because the paper is folded into waves. It is about 1.54 for A flute, 1.43 for C, 1.32 for B, 1.27 for E and 1.25 for F. Multiply the medium GSM by it to find what the medium adds to board weight: 120 GSM on B flute adds about 158 g/m².
A liner runs through the corrugator flat, so one metre of liner makes one metre of board. The medium does not: it is pulled through heated corrugating rolls and formed into a wave, and a wave is longer than the straight line it spans. The take-up factor is that ratio — medium length divided by board length. A C-flute medium with a factor of 1.43 uses 1.43 m of paper for every metre of board that leaves the machine.
The factor depends on flute height and pitch. Tall, widely spaced flutes use the most paper: A flute (4.5–4.8 mm high) is about 1.54. C flute (3.5–3.7 mm) is about 1.43, B flute (2.4–2.6 mm) about 1.32, E flute (1.1–1.3 mm) about 1.27 and F micro-flute about 1.25. These are working figures; the exact value varies slightly with the corrugating roll profile and the mill, so a converter quoting 1.30 or 1.35 for B flute is within the normal spread.
Its main use is calculating board grammage, which is what a box plant charges for. Board GSM = sum of the liner GSMs + sum of (each medium GSM × its take-up factor) + roughly 10 g/m² of starch per fluted layer. A 3-ply C-flute board written 150/120/150 is 150 + (120 × 1.43) + 150 + 10 ≈ 480 g/m², not the 420 g/m² a simple sum suggests — the gap is about 13%, and it is where most disputes over invoiced box weight come from.
Flute choice therefore moves cost as well as performance. The same 120 GSM medium contributes about 185 g/m² on A flute and 152 g/m² on E flute. A 5-ply paper line of 150/120/120/120/150 comes to about 770 g/m² in BC flutes, about 796 g/m² in AC and about 757 g/m² in BB. When two box quotations on the same paper line differ in weight per box, check the flute combination before suspecting the paper.
The take-up factor applies only to the fluted layers. Liners are always counted at face value, and the factor says nothing about strength — a higher take-up means more paper in the flute, which helps flat crush and edge crush, but the strength figures still have to be tested. Use the box size and weight calculator to turn board grammage into weight per box.
Take-Up Factor at a glance
| Definition | Medium length ÷ board length |
|---|---|
| A flute | ≈ 1.54 (4.5–4.8 mm high) |
| C flute | ≈ 1.43 (3.5–3.7 mm high) |
| B flute | ≈ 1.32 (2.4–2.6 mm high) |
| E flute | ≈ 1.27 (1.1–1.3 mm high) |
| F flute | ≈ 1.25 (0.7–0.8 mm high) |
| Board GSM formula | Σ liners + Σ (medium × take-up) + starch |
| Example | 150/120/150 C flute ≈ 480 g/m² |
Common questions
What is the take-up factor of B flute?
About 1.32. One metre of B-flute board uses about 1.32 m of fluting medium, so a 120 GSM medium on B flute contributes 120 × 1.32 ≈ 158 g/m² to the board. Converters quote values between roughly 1.30 and 1.35 depending on their corrugating rolls.
What is the take-up factor of E flute?
About 1.27. E flute is short and closely pitched, so it uses less extra paper than the larger flutes: a 120 GSM medium on E flute adds about 152 g/m² to the board, against 185 g/m² on A flute.
How is the take-up factor used to calculate board GSM?
Add every liner at its own GSM, add each medium multiplied by its take-up factor, and add about 10 g/m² of starch per fluted layer. For 150/120/150 on C flute that is 150 + 171.6 + 150 + 10 ≈ 480 g/m².
Does a higher take-up factor make a stronger box?
It puts more paper into the flute, which tends to raise flat crush and edge crush, but it also makes the board heavier and more expensive. Strength still has to be confirmed by test — the take-up factor is a weight and cost figure, not a strength rating.
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