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Bollard Pull Calculator: Tow Resistance, Tug Requirement & Towing Gear Capacity Tool | ShipUniverse

Harbour Towage • Dead-Ship Assist • Environmental Resistance • Effective Bollard Pull • TOW • Towline MBL • Tug Package

Bollard Pull Calculator: Tow Resistance, Tug Requirement & Towing Gear Capacity Tool

Estimate environmental and tow resistance, convert certified static bollard pull into useful operating pull, determine tug requirement and screen towline, chock, shipboard fitting and tug load-path capacity. Simple mode gives the core answer fast. Advanced adds directional wind/current loads, shallow-water effects, individual tug derating, local port requirements, towing gear and sensitivity analysis.

Figures represent
↑
Need much more depth? Click Advanced above.Advanced adds vessel frontal/side areas, load angles, tow speed, drag coefficients, shallow-water and wave/interaction allowances, individual tug rows, local port minimums, TOW/chock/towline checks and tug-hire cost.
Fast10 primary inputs
Core answerRequired BP + tug count + gear
TransparentBroadside screen + disclosed defaults

Fast Tug Requirement Screen

Simple mode treats design wind and current as broadside control loads, adds your entered tow/manoeuvring resistance, then applies a 20% target pull reserve. Use Advanced for actual load directions and vessel-specific coefficients.

m² broadside.
m² broadside.
knots.
knots.
kN for tow-speed, bank, wave or approved external allowance.
tonnes-force.
% of static BP after speed / weather / geometry losses.
tf TOW / approved working load per tug load path. 0 disables gear gate.

Operation & Vessel

m.
m.
m.
t, contextual only in this drag screen.
Context for entered shallow-water derating.

Projected Areas & Drag Inputs

Use vessel-specific coefficients or approved tug-assist/model-test data when available. The projected-area model is a screening calculation.

m².
m².
m².
m².

Wind, Current & Tow-Speed Resistance

knots.
0° head/on-axis, 90° beam.
knots.
knots. 0 for static hold/control.
kN. 0 uses wetted-area screen below.
m².
Screening coefficient only.
kN from tow plan / engineering allowance.
kN.
% applied to current + tow-speed components.
% above calculated steady design resistance.

Selected Tug Package

tf.
%.
%.
%.
%.
% of summed effective pull usefully combined.
selected currency per tug-hour.

Advanced Tug Fleet Register

Optional. Select “Individual tug register” above to use these rows. Each tug is derated independently. No tug names are collected.

TypeBP tfAvailableSpeed %Weather %Angle %Wash %Max line tfLine MBL tfHire / h

Towline, Chock & Shipboard Towing Fittings

For normal towing, use the marked TOW and approved towing/mooring arrangement plan. Do not substitute a mooring-only SWL for a towing rating unless the approved plan explicitly permits it.

tf per load path. 0 disables.
tf. 0 disables.
tf. 0 disables.
tf.
% from owner / maker / tug operator.
tf from approved arrangement plan where known. 0 disables.

Port / Tow Plan Requirements & Cost

0 = none entered.
tf. 0 = none entered.
hours.
hours.

Tow Plan Readiness

Operational limitation: static bollard pull is not the same as useful force at the assisted ship. Tug propulsion type, vessel speed, towline angle, interaction, sea state, current, UKC, working position and tug safety can materially reduce available force. Escort/indirect towing, exposed-ocean tow engineering and emergency towing require separate approved analysis.
Regulatory / guidance context: SOLAS II-1/3-8 and IMO MSC.1/Circ.1175 guidance address shipboard towing/mooring equipment for normal operations. MSC.1/Circ.1175/Rev.1 applies to ships constructed on or after 1 January 2024; IMO approved Rev.2 in 2025 for ships constructed on or after 1 January 2028. Under Rev.1, supporting hull structure for normal towing is designed for 1.25 times the intended maximum towing load, while the marked TOW is the safe towing load of the shipboard fitting. That structural design factor is not used here as an operational tug reserve. IMO MSC.1/Circ.1101/Rev.3 directs port and tug users to consider required bollard pull, environmental limits, interaction/shallow-water effects, tug capability and towing equipment. Approved plans, port rules, pilots, tow masters, tug certificates and actual marked TOW limits control.
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By the ShipUniverse Editorial Team — About Us | Contact