Sailing Tools & Calculators
Free, practical calculators for every passage — size up your hull speed and sail area, resolve the true wind, set the right anchor scope, read the tide by the rule of twelfths, and measure the miles ahead.
⛵ Hull Speed Calculator
Find a displacement hull's theoretical top speed from its waterline length (feet or metres) — hull speed in knots, mph, and km/h, using the classic 1.34 × √LWL rule
🌊 Sail Area Calculator
Work out mainsail and foretriangle area from your P, E, I, and J rig dimensions, then the total working sail area and the sail-area/displacement ratio that gauges a boat's power
💨 True Wind Calculator
Turn the apparent wind on deck into the true wind over the water from your boat speed and apparent wind angle — true wind speed in knots and true wind angle in degrees
⚓ Anchor Scope Calculator
How much rode to pay out for a secure hold: enter water depth, bow-roller height, and tidal rise, pick your scope ratio, and get the rode length in feet and metres
🌊 Tide Height Calculator
Estimate the water level between high and low water with the sailor's rule of twelfths — enter the two heights and the hours into the tide to see how far it has fallen
🧭 Sailing Distance Calculator
Measure a great-circle passage between two waypoints in nautical miles, kilometres, and statute miles, then estimate passage time from your average boat speed