Ship Trim, Draft Change & Longitudinal Balance Tool

Draft Survey • Cargo Weight • Six Drafts • Perpendicular Correction • Hog/Sag • Trim • Density • Deductibles

Draft Survey Calculator: Cargo Weight, Trim & Density Correction

Estimate cargo loaded or discharged from before-and-after vessel displacement. Simple mode gives a fast cargo-weight screen from ship-table displacement, trim correction, density and deductibles. Advanced performs six-draft reduction, corrections to perpendiculars, selectable hull-deflection treatment, first and second trim corrections, density correction, deductibles and survey-quality diagnostics.

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Need much more depth? Click Advanced above.Advanced adds six port/starboard draft readings, draft-mark offsets, corrections to perpendiculars, 6:1:1 / 4:1:1 / custom hull-deflection methods, LCF and Nemoto trim corrections, structured deductibles, density checks and a survey action board.

Fast9 primary inputs

Core answerCargo loaded or discharged

Transparent1.025 t/m³ table basis disclosed

Fast Cargo Weight Screen

Use ship-table displacement extracted for each survey condition. Enter the total signed trim correction from the vessel calculation or approved table. Simple mode applies density and changes in non-cargo deductibles.

Initial survey

Table displacementtonnes, before density correction.

Total trim correctiontonnes, signed. Positive adds to displacement.

Measured dock-water densityt/m³, apparent density used for draught survey.

Total variable deductiblestonnes. Ballast, bunkers, FW, LO and other non-cargo changes.

Final survey

Table displacementtonnes, before density correction.

Total trim correctiontonnes, signed.

Measured dock-water densityt/m³.

Total variable deductiblestonnes.

Reference shore / B/L quantity optionaltonnes. Used only to show a difference, not to judge an automatic pass/fail.

Vessel & Calculation Basis

Use the sign conventions shown below consistently with the vessel’s approved hydrostatic information.

Length between perpendiculars (LBP)metres.

Hydrostatic reference densityt/m³. Common salt-water basis is 1.025.

Hull-deflection / adjusted mean method

Custom deflection factorUsed only for custom-factor mode: AMD + factor × (Mid − AMD).

Trim correction method

Reference shore / B/L quantityoptional tonnes.

Draft-Mark Positions

Offset sign convention used by this tool: enter a positive offset when the draft mark is forward of its reference station (FP, midships or AP), and a negative offset when it is aft. Trim is positive by the stern. LCF is positive aft of midships and negative forward of midships.

Forward mark offsetm from FP.

Midship mark offsetm from midships.

Aft mark offsetm from AP.

Initial Survey

Six observed drafts

Forward port

Forward starboard

Midship port

Midship starboard

Aft port

Aft starboard

Hydrostatics at the calculated adjusted mean draft

Measured dock-water density

Table displacementtonnes, extracted/interpolated from approved hydrostatics.

TPCtonnes/cm.

LCF from midshipsmetres. + aft, − forward.

MCTC at adjusted mean − 0.5 mt·m/cm.

MCTC at adjusted mean + 0.5 mt·m/cm.

Approved-table total trim correctiontonnes. Used only if approved-table method is selected.

Final Survey

Six observed drafts

Forward port

Forward starboard

Midship port

Midship starboard

Aft port

Aft starboard

Hydrostatics at the calculated adjusted mean draft

Measured dock-water density

Table displacement

TPC

LCF from midshipsmetres. + aft, − forward.

MCTC at adjusted mean − 0.5 m

MCTC at adjusted mean + 0.5 m

Approved-table total trim correction

Non-Cargo Deductibles

Enter tonnes present at each survey. Permanent lightship need not be re-entered in a before-and-after survey because it cancels. A ship constant may be included if it is part of the agreed survey method.

Deductible type	Initial t	Final t

Survey Readiness

Draft marks readable and agreedSix readings taken carefully and recorded. Drafts and density taken togetherConditions did not materially change between readings. No weight movement during surveyCargo, ballast, bunkers and FW were controlled. Density sampling representativeSamples taken clear of discharges and stagnant water. Draught-survey hydrometer verifiedInstrument type, condition and calibration considered. Tank quantities correctedSounding tables, trim/list and ballast density reviewed. Hydrostatic data verifiedUnits, reference density and sign conventions checked. Other weight changes accountedBunkers, stores, anchors, bilges, sludge and deliveries reviewed.

Calculation inputs may be stored to improve Ship Universe tools. Benchmark participation is separate. Privacy Policy.

Survey limitation: a draught survey is a measurement-based commercial quantity assessment, not an exact weighing system. Accuracy depends on draft readings, hull deflection, approved hydrostatics, water-density sampling, tank soundings, trim/list corrections and accounting for all weight changes. The vessel’s approved documentation and the agreed survey procedure control the final signed result.

Methodology context: the calculation chain follows established draught-survey practice reflected in UN ECE ECE/ENERGY/19 and P&I guidance: before-and-after displacement, corrections to perpendiculars, hull-deflection treatment, trim correction, density correction and non-cargo deductibles. The 6:1:1 mean-of-means method is not treated as universal; Advanced also includes a fuller-form 4:1:1 option and a vessel-specific factor method. Use the ship’s approved hydrostatic and tank data, sign conventions and any approved trim-correction tables where provided.

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Ship Trim, Draft Change & Longitudinal Balance Tool

Draft Survey Calculator: Cargo Weight, Trim & Density Correction

Fast Cargo Weight Screen

Vessel & Calculation Basis

Draft-Mark Positions

Initial Survey

Final Survey

Non-Cargo Deductibles

Survey Readiness