Bollard Pull Calculator -

The Bollard Pull Calculator is a handy tool for the maritime industry, providing precise calculations for towing forces. It is essential for ship design, port navigation, and towing operations. With its sophisticated algorithms and parameters, the calculator accurately determines bollard pull force, enabling maritime professionals to ensure safety and efficiency in vessel operations. Elevate your maritime ventures with the Bollard Pull Calculator's comprehensive features and capabilities


A handy and simple tool to determine in a minimum time what is really needed as tug assistance, is the "Bollard Pull Calculator" which calculates in an approximate way the total required tug power for ships in various conditions of wind and current. This tool can be loaded as an app on the smart phone.

The tool is based on the calculations and graphs as explained in chapter 5 of  the book “Tug Use In Port”, written by Captain Henk  Hensen FNI; The Nautical Institute, London, UK, with a 3rd edition published by The ABR Company, UK ( 2018). Moreover, formulas of linear and non-linear regressions obtained from academic and scientific studies have been digitalized and made suitable for mobile application. (BS 6349-1, OCIMF  Mooring Equipment Guidelines (MEG4) 4th Edition 2018, SIGTO’s Prediction of Wind Loads on Large Liquefied Gas Carriers (2007), Post-Panamax Full Loaded Cond. Jare, Andersen I.M.V. (2003), Parameter identification of wind loads on ships, Werner BLENDERMANN [1993])


Assumptions Values & Coefficients for wind Calculations

* Density of air in kg/m³ is assumed as 1,28

* The wind drag coefficients assumed the trim is zero in the fully loaded condition and 0.8 degrees in the ballast condition.

* Wind drag coefficients (nonlinear diagrams) of VLCC (laden or in ballast)/Prismatic & Sypherical Gas Carrieers

in determined by wind tunnel tests are taken from OCIMF MEG4. (The wind coefficients are based on data obtained from wind tunnel tests

 conducted at the University of Michigan in the 1960s.)

The wind coefficient values are based on a comprehensive set of wind tunnel tests conducted on prismatic and spherical gas

 carriers for SIGTTO's Prediction of Wind Loads on Large Liquefied Gas Carriers (2007). Model tests covered the following sizes:

Spherical 125,000, 135,000 and 150,000m³ / Prismatic 75,000,135,000 to 155,000, 210,000 and 260,000m³

* Wind drag coefficients (nonlinear diagrams) of "General cargo/Container" in determined by wind tunnel tests

(Post-Panamax Full loaded cond.)are taken from Andersen I.M.V. 2003

* Wind drag coefficients (nonlinear diagrams) of "PCC/CRUISE LINER" are taken from W.Blendermann,1994/2014

* Wind drag coefficients (nonlinear diagrams) of "DRILL SHIP", "FISHING/CUTTER", "DIVER/RESEARCH/OFFSHORE SUPPLY VESSEL"


Assumptions Values & Coefficients for Current Calculations

* Density of sea water in kg/m³ is assumed as 1025

* The trim is assumed to be zero for all the current drag data and the effects of trim on current coefficients were not investigated.

(However, the effect of trim will be most pronounced for the yaw current coefficients for ballasted tankers in shallow water.)

* Current drag coefficients (nonlinear diagrams) of VLCC (laden or in ballast)/Prismatic & Sypherical Gas Carrieers

are taken from OCIMF MEG4.The current coefficients are the result of Computational Fluid Dynamics (CFD) modelling,

performed by Lloyd's Register on behalf of OCIMF, and have been extracted from a 2017 report  on that work.

(Full scale CFD modelling run on ships of 50,000,150,000 and 300,000 DWT.)

IMPORTANT NOTE: Please note that data provided by the application are based on theoretical calculations.
The calculations give an indication of the required bollard pull and should always be handled with care.

This tool has been developed for informational use only and cannot be used as a direct reference when performing ship manoeuvres.