Free Naval Architecture &amp; Marine Engineering Calculators

Learn how principal dimensions and coefficients shape early-stage vessel design decisions.

Holtrop-Mennen Resistance Method

Theory, formulas, and application notes.

Walk through the resistance components and practical limits behind the method.

Effective, delivered, shaft, and brake power.

Marine Power Chain

Understand how hull resistance becomes propeller demand, engine power, and installed power.

EEOI and Fuel Consumption

Fuel use, transport work, and carbon efficiency.

See how fuel burned, cargo carried, and voyage distance shape operational carbon performance.

Industry-standard resistance prediction.

Popular Calculators

Fast entry points for the checks engineers and students tend to need first.

Holtrop-Mennen

Power to overcome resistance.

Effective Power (PE)

Engineering unit conversions.

Unit Converter

How “full” the underwater volume is.

Browse Calculators

Full calculator menu with category filters available from the top ribbon.

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Hull Design

Core hydrostatics & hull-form coefficients used in early-stage design and comparisons.

Block Coefficient (CB)

Calculates CB from principal dimensions and displacement volume to quantify hull fullness.

Midship section “efficiency”.

Midship Coefficient (CM)

Relates midship sectional area to B×T to evaluate section fullness.

Prismatic Coefficient (CP)

Volume distribution along length.

Computes CP from displacement volume, L and midship area to support resistance trends.

Waterplane Coefficient (CWP)

Waterplane “fullness”.

Finds CWP as AWP / (LWL × BWL), useful for stability & seakeeping intuition.

Mass/weight from volume & density.

Displacement

Convert between displacement volume and mass using seawater/freshwater density.

Waterplane Area (AWP)

Area at the waterline.

Estimate AWP for hydrostatics and stability calculations.

Wetted Surface Area (WSA)

Skin friction driver.

Compute WSA to support frictional resistance estimates and scaling checks.

Longitudinal centre of buoyancy.

LCB

Locate buoyancy centre along length to support trim/balance checks.

Longitudinal centre of flotation.

LCF

Find the pivot point for small trim changes (important for trim/MCT logic).

Bulbous Bow Volume & Area

Bulb geometry helpers.

Quick bulb metrics used in preliminary resistance discussions.

Industry-standard resistance prediction.

Resistance

Estimate calm-water resistance with commonly used empirical/semi-empirical methods.

Holtrop–Mennen

Planing hull resistance approach.

Savitsky (Planing)

Trim, lift and resistance estimates for planing craft.

Alternative resistance estimator.

Telfer

Empirical resistance estimation method for preliminary checks.

Speed-based approximation.

Froude Estimator

Quick resistance estimates using ITTC friction + residual assumptions.

Scaling & correlation tools.

Model–Ship Correlation

Convert model data to full-scale using standard correlation practices.

Generate a curve from assumptions.

Speed–Power Curve

Build a speed–power relationship using resistance estimates and efficiencies.

Advance vs actual travel.

Propulsion & Power

Translate resistance into effective, delivered and brake power — and evaluate key efficiency factors.

Propeller Slip

Compute slip percentage from pitch, RPM and vessel speed.

Propeller Efficiency (η₀)

Open-water efficiency.

Evaluate η₀ from thrust/power relationships (as per your calculator logic).

Wake/thrust deduction effect.

Hull Efficiency (ηH)

Compute hull efficiency from wake fraction and thrust deduction.

Relative Rotative Efficiency (ηR)

Behind-hull prop effects.

Compare behind-hull and open-water performance.

Power to overcome resistance.

Effective Power (PE)

Popular

Compute PE from resistance and speed.

Convert effective power to delivered power using efficiency chain.

Delivered Power (PD)

Power at the shaft/prop.

Power

Engine output requirement.

Brake Power (PB)

Power

Estimate PB from PD and drivetrain efficiencies.

Initial transverse stability.

Stability & Load

Initial stability, trim, free surface effects, and longitudinal balance helpers.

Evaluate GM and basic initial stability indicators.

Longitudinal balance estimate.

Trim

Trim and longitudinal balance checks for loading changes.

Free Surface Correction (FSC)

Slack tank stability loss.

Apply FSC to account for reduced GM due to free surface in tanks.

MCT 1 cm

Moment to change trim.

Estimate MCT 1 cm for trim change calculations.

Righting arm curve tools.

GZ Curve Generator

New

Generate and interpret a GZ curve based on stability inputs.

Record vessel fuel use, calculate CO2 emissions, track MRV scopes, and export reports.

Fuel & Machinery

Fuel consumption, engine efficiency, emissions, and operational performance tools.

MRV CO2 Recorder

Voyage emission logbook.

New

Open Recorder

Fuel Consumption

Engine fuel usage estimate.

Estimate fuel consumption based on power, speed, and operating time.

Specific fuel efficiency.

SFOC

Analyze specific fuel oil consumption for marine engines.

Fuel Cost

Voyage cost estimation.

Calculate total fuel costs using consumption rates and fuel prices.

CO₂ Emissions

Carbon output estimate.

Estimate CO₂ emissions based on fuel type and consumption.

Operational efficiency index.

EEOI

Evaluate Energy Efficiency Operational Indicator for voyages.

Identify optimal operating speed for fuel and emission efficiency.

Engineering unit conversions.

General Utilities

Quick helpers used across engineering workflows.

Unit Converter

Percent change and ratios.

Percentage

Compute percent difference, increase/decrease, and ratio-based outputs.

Add or subtract durations and compute date differences.

Interpolate between points.

Linear Interpolation

Quick linear interpolation for tables and curves.

Reynolds Number

Flow regime quick check.

Compute Reynolds number for basic hydrodynamic reasoning.

Density Converter

Common density units.

Convert density between kg/m³, g/cm³ and other common units.