What this calculator does
Hull speed (displacement boat) works out the theoretical top speed of a displacement-hull boat from its waterline length. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaV = 1.34 × √(waterline length in feet), V in knots
The inputs explained
| Field | What to enter |
|---|---|
| Waterline length (ft) | A number, measured in ft. Starts at 30. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with waterline length
Every other input is held at the calculator’s starting values while waterline length varies. Select any row to load that scenario into the calculator.