Mean / True Mean Draft

Mean draft and UNCTAD 'mean of means' draft at the LCF - the reference every draft-survey starts with.

StabilityDraft survey

Draft marks

Forward draftmAft draftmMidships draftmRead from both port and starboard and average.

Geometry

LCF distance from APmFrom hydrostatic tables at the current mean draft.Length between perpendicularsm

Mean draft (F + A)/2: 6.800m

Mean of means (F + A + 6M)/8: 6.815m

Corrects for hog/sag.

True mean at LCF: 6.800m

Trim: 0.600m

By the stern

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

T_{MoM} = \tfrac{T_F + T_A + 6 T_M}{8}, \quad T_{LCF} = T_{mean} + \text{Trim} \cdot \left(\tfrac{LCF}{L_{pp}} - \tfrac{1}{2}\right)

Symbol	Meaning	Unit
$T_F, T_A, T_M$	Forward, aft, midships draft	m
$LCF$	Long. centre of flotation from AP	m
$L_{pp}$	Length between perpendiculars	m
$Trim$	Aft − fwd draft (stern positive)	m
$T_{LCF}$	True mean draft at LCF	m

Source: UNCTAD - *Draft survey guidelines* (1991); Derrett & Barrass

In short

Mean draft, mean-of-means and UNCTAD true mean draft at LCF.

Learn the theory Intact stability