How to Calculate a Blanket's Starting Chain

Why "Chain Until It Looks Wide Enough" Fails

One of the most persistent myths passed between crafters is that you can simply chain across your bed or lap until the foundation chain "looks about wide enough."

This technique fails for two concrete reasons:

Foundation chains compress when worked: When you work your first row of stitches into a chain, the chain loop structure draws yarn upward into stitch posts, causing the chain to shorten noticeably horizontally compared to its slack pre-stitched state.
Pattern stitch repeats: Almost all textured blanket patterns (waffle, ripple, moss stitch, shells) require a whole-number multiple of stitches. If your chain ends on an arbitrary count, your pattern motif will be cut off awkwardly at the far edge.

Step 1: Separate Finished Width from Inner Target Width

If your blanket will feature a border (e.g. a simple ribbed border or multiple rounds of moss stitch), that border adds width to both the left and right sides of your blanket:

W_inner = W_finished - (2 × Border Width)

Worked example: Suppose you want an estimated finished throw blanket width of 120 cm and plan to add a 5 cm border around the edges. The inner fabric worked in the main pattern must target:

120 cm - (2 × 5 cm) = 110 cm inner target width.

Inner stitch count determines fabric width; border width is added to both left and right sides.

Explanatory Schematic: Border Deduction & Inner Repeat Width

The vector diagram above illustrates how left and right side borders (5 cm each) reduce a 120 cm total target width to a 110 cm inner panel for repeating stitch motifs.

Step 2: Calculate Unconstrained Stitches from Measured Gauge

Using the stitch gauge measured from your test swatch, determine how many stitches would theoretically produce your inner target width:

Raw Target Stitches = Inner Width × (Stitches Counted ÷ Swatch Width)

Continuing the worked example, if your swatch yielded 18 stitches per 10 cm (1.8 stitches per cm), your 110 cm inner target requires:

110 cm × 1.8 st/cm = 198.0 raw target stitches.

Step 3: Fit the Pattern Repeat Formula (S = n × m + e)

Look closely at your pattern notes. A pattern written as "multiple of 6 + 2" means:

Repeat multiple (m): 6 stitches per repeating motif.
Extra stitches (e): 2 edge stitches added once to balance the row.

To find the number of repeats n that closest matches your 198 raw target stitches:

Subtract the extra stitches: 198 - 2 = 196.
Divide by the multiple: 196 ÷ 6 = 32.67 repeats.

Because 32.67 is not a whole number, you have two neighboring whole-repeat options:

Option A (32 repeats): 32 × 6 + 2 = 194 stitches. At 1.8 st/cm, this gives an estimated inner width of 107.8 cm (estimated finished width with borders: 117.8 cm).
Option B (33 repeats): 33 × 6 + 2 = 200 stitches. At 1.8 st/cm, this gives an estimated inner width of 111.1 cm (estimated finished width with borders: 121.1 cm).

Option B is within 1.1 cm of the 120 cm target, making 200 first-row stitches the closer repeat-compatible option.

Step 4: Determine the Starting Foundation Chain (C = S + c)

Do not assume your foundation chain equals your first-row stitch count! You must add the specific foundation chain offset c required by your pattern's starting stitch:

If the pattern directs: "Dc in 4th chain from hook (counts as 1st dc)", the offset c is +2 (because 1 chain provides stitch body and 2 chains provide turning height).
If the pattern directs: "Sc in 2nd ch from hook", the offset c is +1.

If your selected first-row count S is 200 stitches and your pattern specifies an offset c = 2, your starting chain is:

Starting Chain C = 200 + 2 = 202 chains.