Simple calculators and converters that work instantly in your browser, with no sign-up.
- Sail Performance CalculatorCalculate displacement/length ratio, sail area/displacement ratio, capsize screening value and hull speed from a boat's dimensions.
- Nautical Unit ConverterConvert knots, mph, km/h and m/s, or nautical miles, miles, kilometres, metres and feet, instantly.
- HTML Math Equation GeneratorTurn simple shorthand into HTML entity code for integrals, sums, fractions, roots and other math symbols, with a live preview.
Plan the passage
- Passage Time CalculatorEnter distance and average speed to get passage duration and arrival time for any boat leg.
- Beaufort Scale to Knots ConverterTurn a Beaufort wind force into knots, km/h, mph and sea state, or find the force for any wind speed.
- Anchor Scope CalculatorEnter water depth, bow height, tide allowance and scope ratio to get the anchor rode length to let out.
Convert units
- US to Metric ConverterConvert US and British units of length, weight and volume to metric and back, instantly.
- Number Base ConverterConvert a number between decimal, hex, octal, binary and base32 as you type.
Calculate and code
- Online CalculatorType or tap an expression and get the result instantly, with square roots, powers, trigonometry, logarithms and factorials.
- Calculator with Paper TapeAn adding-machine style calculator that records every entry and running total on a paper tape, with degrees and radians modes.
Teach and test
- Multiple Choice Test MakerType questions and options, mark the right answer and get a formatted printable test with an answer key.