Free Maritime Calculators
Select a specific calculator below.
Ship Squat Effect Calculator (Barras 2004)
Professional estimation of maximum bow squat using the Barras (2004) formula. Supports open-water and confined-channel modes with Blockage Factor S.
Distance, Speed & Time (DST)
Enter any two values to calculate the third. Useful for quick ETA estimations and passage planning.
Distance to Horizon & Radar Range
Calculate visual horizon distance and radar horizon range based on Height of Eye above sea level.
Linear Interpolation Table
Calculate exact intermediate values from hydrostatic tables, tide tables, or any set of tabulated data.
Under Keel Clearance (UKC) Calculator
Calculate net UKC from charted depth, tide height, ship draft, estimated squat, and required safety margin.
FWA & DWA Calculator
Calculate Fresh Water Allowance (FWA) and Dock Water Allowance (DWA) for load-line operations.
True Wind Calculator
Convert Apparent Wind Speed & Direction plus ship's Course/Speed into True Wind Speed and Direction using vector mathematics.
Tidal Height Calculator (Rule of Twelfths)
Estimate tidal height at any point in the tidal cycle using the Rule of Twelfths approximation. Enter LW and HW heights from tide tables.
CPA / TCPA Calculator
Calculate closest point of approach and time to CPA from own ship and target motion data for a quick collision-avoidance check.
Set & Drift Calculator
Combine course through water, speed through water, current set and current drift to estimate resulting COG and SOG.
Mean Draft & Trim Calculator
Calculate mean forward draft, mean aft draft, overall mean draft and trim from port and starboard draft readings.
Air Draft & Bridge Clearance Calculator
Estimate bridge clearance from charted bridge height, tide, air draft, dynamic allowance and safety margin before transit.