Draft & Trim Calculator
Calculate how loading affects draft and trim
Added Weight
Draft & Trim Results
New Mean Draft
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Draft Change
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Trim Angle
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Bow Draft Change
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Stern Draft Change
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New Displacement
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Tons Per Inch (TPI)
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Moment to Trim 1"
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Common Loading Weights
| Item | Typical Weight |
|---|---|
| Water (per gallon) | 8.3 lbs / 3.8 kg |
| Diesel Fuel (per gallon) | 7.1 lbs / 3.2 kg |
| Gasoline (per gallon) | 6.1 lbs / 2.8 kg |
| Person (average) | 175 lbs / 80 kg |
| Outboard Motor (per HP) | ~3-5 lbs |
About Draft & Trim Calculations
Tons Per Inch (TPI): The weight required to change draft by one inch. TPI = (LWL x Beam x Cb) / 420 for salt water, where Cb is block coefficient (typically 0.35-0.65 for yachts).
Trim: The difference between forward and aft draft. Adding weight forward of the center of flotation trims the bow down, and vice versa.
Moment to Trim (MTT): The moment (weight x distance) required to change trim by one inch. MTT = Displacement x GM_L / (12 x LWL) approximately.
Note: These are simplified estimates assuming a box-shaped hull. Actual values depend on hull shape. For precise loading calculations, consult your vessel's stability booklet.