Hull Speed
Wind Chill
Battery Capacity
All conversions
Icebox Calculations

Distance between 2 points


Theoretical Maximum Hull Speed:
   Each style of boat hull has a theoretical maximum speed that it is capable of attaining. For displacement hulls (traditional style yachts, non-planing motor boats) the maximum hull speed is a function of the volume of water displaced along the boat's waterline length.
This theoretical max speed is due to the sharp increase in wave-making resistance at high speeds. If you could exceed this theoretical speed by a substantial margin without planing, the bow and stern waves would be higher than the freeboard and the vessel would probably sink. 
When a boat is moving at its optimum hull speed, the bow & stern wakes will combine into a single wake for the boat.

Although any boat may exceed this speed for short periods of time, on long offshore passages with cruising boats and/or short handed crews this level of performance is rarely reached.


Waterline length (feet) =

light displacement yacht =
large displacement yacht =
multihulls =

These calculations are for vessels with waterline lengths of approx 25 to 50 feet. Larger vessels  may experience faster passages than predicted and smaller vessels could be slower.

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Wind Chill:
   A measure of the cooling effect of wind. Wind increases the rate at which a body loses heat, so the air on a windy day feels cooler than the temperature indicated by a thermometer. This heat loss can be calculated for various combinations of wind speed and air temperature and then converted to a wind chill equivalent temperature (or wind chill factor).   
Wind Speed =
Air Temperature =


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Battery Capacity:
   Deep Cycle batteries are generally used to supply the boat's "household" power and are measured in Amp-Hours (AH or Ah). 

Typical power usage:
  low power lights = 1 Amp
  nav lights = 3 Amps
  laptop computer = 5 Amps
  ice box = 5 Amps
  small pumps = 3 Amps
  heavy duty pumps = 5 Amps

To calculate your "daily energy use: for each appliance, multiply the Amps by the number of hours each day that it is used. Add all these daily "Amp Hours" used together, then multiply the total by your system voltage (ie: 12,24,240 etc) this figure is your daily "Watt Hour" energy usage.

NOTE: CCA (Cold Cranking Amps) Batteries are used for starting the engine. The quoted CCA value will deliver that many amps for 30 seconds such that the resultant battery voltage will not fall below 7.2V (measured at 0F)


Daily energy use Watt/hours
Number of days storage desired days
Loss factor
(50% typical)
Discharge depth factor

System Voltage

Capacity (Amp hrs)
12 Volt Amp hours
24 Volt  Amp hours
48 Volt  Amp hours
110 Volt  Amp hours
240 Volt  Amp hours

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Great Circle Distance between two points
(Points A and B as Latitude & Longitute)

Point A location: 

 Latitude A: (decimal) or (deg/min/sec) '''
Longitude A: (decimal) or (deg/min/sec) '''

Point B location: 

 Latitude B: (decimal) or (deg/min/sec) '''
Longitude B: (decimal) or (deg/min/sec) '''

Distance from Point A to Point B is nautical miles

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Press the top row of buttons to select the class of conversion you want,
then type in a value and select a unit for conversion.

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Marine Refrigerator Box Assistant

Builder's Calculator

The Box Builder's Calculator will determine the amount of "usable" interior volume in a variety of box shapes based on the total gross space available and the insulation thickness.  

This calculator assumes that you have a fixed gross volume  in which to build a box and reduces the usable interior space as you increase the insulation thickness.

The heat load given is for daily use of the box by a live-aboard couple in a tropical climate.

Select the area which most closely resembles space in which you plan to build your box.


Heat Load Calculator

The Heat Load Calculator will quickly estimate the amount of heat which will enter your box as well as the total interior volume.  

This calculator assumes that the inside box volume stays constant and that you are adding the insulation to the outside of the box liner (ie. adding insulation increases the gross space required but does not reduce the inside volume). 

The heat load given is for daily use of the box by a live-aboard couple in a tropical climate.



Select the box below which most closely resembles your own.


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