Vertical Bust Darts Calculator

Vertical Bust Darts Calculator

Vertical bust darts add width around the bust by increasing at the side markers, holding that width across the full bust, then decreasing back. Enter your gauge and a few measurements and the calculator returns the exact written instructions, ready to drop into your pattern.

1. Which measuring system are you using?

2. What is your gauge?

3. Which garment are you making?

4. Which direction are you knitting?

This sets which way each increase leans. The same shaping knitted the other direction reads the opposite way, so the left and right markers swap increases.

5. Which increase method are you using?

How to work this increase

6. What is your full bust circumference?

Measured around the fullest part of the bust. Used to size the plain section over the bust, and (if you calculate the ease below) to work out how much width to add.

7. How much width should the darts add?

The total you want to add to the body circumference at the bust.

8. How tall is the bust curve?

The vertical distance the increases are spread over. This is the space between where the bust starts to curve out (upper bust) and its fullest point (full bust), see the schematics below.

9. Where do the darts begin? (bottom-up only, optional)

Optional. Fill these in and the calculator works out how far above the hem to begin, so the shaping lands at your full bust line. For the row count to be right, put your actual (blocked) row gauge in step 2.
Your vertical bust darts

When to work the vertical bust darts

Vertical darts sit at the two side markers. You increase on the way to the full bust, hold the extra width across it, then decrease away again — the placement is the same whichever direction you knit.

Where they go

Begin the shaping the calculated distance before you reach your full bust line, from either side. The increases add the width and the plain section holds it, so your full bust apex sits at the top of that plain section, and the decreases then bring you back to the body count. Because the increase and decrease sections mirror each other, this is true whether you knit top-down or bottom-up — the number is shown in the results above once you fill in your gauge and measurements.

Schematic: upper bust and full bust lines
Upper bust and full bust lines
Schematic: vertical bust dart placement
Yellow arrows show the process of vertical bust darts knitted top-down.
For bottom-up garments, the process is identical only starts at the underbust line and ends at upperbust line.


I strongly recommend blocking a swatch, and ideally the yoke or lower body, before committing to the placement — blocking can noticeably change length and gauge. Without it, the darts may sit too high or too low.

Bottom-up: finding the starting point from the hem

Working bottom-up needs a little more planning, because you reach the full bust line on the way up. You first work out how far the full bust sits above the hem, then subtract the height of the increase section plus the plain section so the shaping reaches your full bust apex exactly.

Example

Your finished body length is 50 cm (19¾"), and your shoulder-to-full-bust measurement is 27 cm (10¾"). Your full bust line therefore sits 23 cm (9") above the hem (50 − 27). The calculator subtracts the increase and plain-section height for you once you enter both measurements in step 9 above.

This only holds if your row gauge matches the pattern gauge. If it changes after blocking, the length changes too, and the starting point must move with it.

Example

Say your blocked gauge is 26 rows per 10 cm (4") instead of the pattern's 27 rows per 10 cm (4"). Your body will now measure roughly 52 cm (20½") instead of 50 cm (19¾"), so you'd begin the shaping a little higher from the hem to keep it aligned with the full bust line.

For the most accurate result, knit about 15 cm (6") of the body, block it, let it dry, and measure your blocked row gauge before deciding where the darts begin. If that feels like a lot, just enter your finished length, your shoulder-to-full-bust measurement, and your actual blocked row gauge into the calculator and it will do the arithmetic for you.