Dart Calculator
Dart intake from a bust and waist difference.
Calculate dart intake for a bodice or skirt from the difference between two measurements, split between darts and side seams.
Intake per dart
2.00"
8.00" to remove in total
Above about an inch and a half of intake a single dart bubbles at the point, especially in crisp fabric. Split it into two shallower darts rather than making one deeper.
How the Dart Calculator works
A dart removes the difference between a larger measurement and a smaller one — bust to waist, hip to waist — so the fabric follows the body instead of hanging straight. The total to remove is fixed by the two measurements; the design decision is how much goes into darts and how much into the side seams.
Also known as: dart intake calculator · dart width calculator
What a dart is doing
A dart removes the difference between two measurements so flat fabric can follow a curved body. The total to remove is fixed — bust minus waist, or hip minus waist — and the design decision is how it is distributed.
Conventionally about half goes into the side seams and half into darts. Too much at the side seams pulls the seam forward and distorts the silhouette from the front; all of it in darts gives very deep darts that bubble.
Each dart's intake is the dart share divided by the number of darts. More, shallower darts shape more smoothly than fewer deep ones, which is why fitted garments often have two waist darts per side rather than one.
A worked example
A 38 inch bust and 30 inch waist means eight inches to remove. Half to the side seams leaves four inches across the darts; over two darts that is two inches each — deep, but workable in a soft fabric.
Splitting the same four inches over four darts gives one inch each, which shapes far more smoothly and is what a fitted bodice in a crisp cotton would want. The total removed is identical; only the distribution changed.
Where the answer misleads
Intake is only half the dart. The length and the point placement matter as much: a dart should stop about an inch short of the fullest part it is shaping, because a dart that reaches the apex produces a visible cone rather than a curve.
Fabric changes what is achievable. A two inch dart that lies flat in wool crepe will bubble in poplin, and the answer is to split it rather than to press harder.
Finally, this assumes symmetry between front and back, and bodies are not symmetrical front to back. The front usually needs more shaping than the back, so an even split between the two is a starting point rather than a rule.
Frequently asked questions
How do I calculate dart intake?
Subtract the smaller measurement from the larger to get the total to remove, decide what share goes to the side seams — half is typical — and divide the rest by the number of darts.
How much should go into the side seams?
About half is conventional. Putting too much into the side seams pulls the seam forward and distorts the silhouette; putting it all into darts gives very deep darts that bubble at the point.
How deep is too deep for one dart?
Above roughly an inch and a half of intake a single dart starts to bubble at the point, particularly in crisp fabric. The usual answer is to split it into two shallower darts rather than to make one deeper.
Where should a dart point?
Toward the fullest part it is shaping, stopping short of it — about an inch from the bust point for a bust dart. A dart that reaches the apex produces a visible cone; stopping short lets the fabric round over it.