Increases and decreases are how crochet gets its shape. Every time you add or remove stitches, your total count changes — and keeping track of that change is what makes the difference between a pattern that works and one that leaves makers scratching their heads.
Here are the three formulas I use when writing and checking patterns.
Increases
When you increase, one base stitch becomes two (or more). Your total stitch count goes up.
Formula 1 — simple increase row
previous row total + number of increases = new total
Example:
- Previous row: SC 12 (12)
- Current row: (SC, inc) × 6
- Calculation: 12 + 6 = 18
- Written as: (SC, inc) × 6 (18)
Formula 2 — increase row with plain stitches
When some stitches get increased and others don't:
(plain stitches × repeats) + (increased stitches × repeats × 2) = total
Or more practically: work out what each repeat produces, then multiply by the number of repeats.
Example: (2 SC, inc) × 6
- Each repeat: 2 SC + 1 inc = 3 stitches worked, producing 4 stitches
- 4 × 6 = 24
Decreases
When you decrease, two (or more) base stitches become one. Your total stitch count goes down.
Formula 3 — decrease row
(stitches with no decrease) + (base stitches − decrease amount) × number of repeats = total
Example: (SC, dec) × 6 starting from 18 stitches
- Each repeat: 1 SC + 1 dec (which uses 2 stitches) = 3 stitches used, producing 2
- 2 × 6 = 12
Or using the simple version of Formula 1 in reverse:
previous total − number of decreases = new total
18 − 6 = 12 ✓
Using the formulas together
These formulas are tools, not rules. The goal is to be able to look at any row in your pattern and confirm: does this instruction produce the stitch count I've stated?
Work through each row in sequence: 1. Start with your known total from the previous row 2. Apply the formula for the current row's instruction 3. Check it matches the count you've written at the end of the row
If it doesn't match — something is wrong with either the instruction or the count. Fix it before moving on.
A practical tip
For complex shaping, write out your stitch count table before you write the pattern instructions. Decide on the counts you want, row by row, then work backwards to figure out what instructions produce those counts. It's much easier than writing instructions first and hoping the math works out.
Stitch count errors are among the most common mistakes in published patterns — and among the hardest for makers to diagnose. Getting the formulas right at the writing stage means less confusion for your testers, fewer revision rounds, and a cleaner final pattern.
If you want these calculations verified automatically, row by row, that's what FFcopilot is built for.