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A list of useful conversions and formula

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What is the issue?
The world's measures are far from standard, and we run multiple measures of temperature, distance, space etc depending upon which activity is being undertaken or which nation we happen to be in.

Why address this?
To make sense of the data we need to use conversion tables.

How to address this?
Here is a list of useful conversion tables that may turn out to be useful.


To convert degrees Celsius into degrees Fahrenheit….Multiply by 1.8 and add 32
To convert degrees Fahrenheit to degrees Celsius….Subtract 32 and divide by 1.8


To convert Pounds (Ib) to Kilogrammes (kg) ....multiply by 0.4536
To convert Kilogrammes to Pounds .....multiply by 2.205

Water 1 litre weighs 1.00 kg/2.2 lb.
1 gallon weighs 4.53 kg/10 lb.


To convert Gallons to Litres ....multiply by 4.546
To convert Litres to Gallons ....multiply by 0.22

To convert Petrol to Weight ....1 litre weighs 0.73 kg/1.61 lb. 1 gallon weighs 3.36 kg/7.4 lb.
To convert Diesel to Weight .....1 litre weighs 0.84 kg/1.85 Ib.1 gallon weighs 3.86 kg/8.5 lb.

Quick conversions:
1 Imperial Gallon = 4.546 litres = 1.2 US Gallons
1 litre = 0.22 Imperial gallons = 0.264 US Gallons
1 US Gallon = 3.8 litres = 0.83 Imperial Gallons


To convert Inches to Centimetres (cm) ....multiply by 2.54
To convert Centimetres to Inches .....multiply by 0.393

Quick conversions
1 foot = 30.48 centimetres (cm)
1 yard = 0.9144 metre (m)
1 mile = 1.6093 kilometres (km)
1 millimetre = 0.03937 inch
1 centimetre = 0.0328 foot (ft)
1 metre = 1.094 yards (yd)
1 kilometre = 0.62137 mile

1 nautical mile = 1852 m
1 International mile = 1609.344 m

Quick and dirty conversions
Metres into yards add one-tenth
Yards into metres deduct one-tenth
Kilometres into miles multiply by 5 and divide by 8
Miles into kilometres multiply by 8 and divide by 5
Litres into pints multiply by 7 and divide by 4
Pints into litres multiply by 4 and divide by 7
Litres into gallons multiply by 2 and divide by 9
Gallons into litres multiply by 9 and divide by 2
Kilogrammes into pounds divide by 9 and multiply bv 20


To convert cubic feet to cubic metres .....multiply by 0.028
To convert 1 cu ft to fluid capacity .....it holds 6114 gallons of water weighing 62.31b
To convert square metres to square feet .....multiply by 10.764
To convert square feet to square metres .....multiply by 0.093
To convert square centimetres to square feet .....multiply by 0.001076
To convert square inches to square centimetres .....multiply by 6.451


1 knot = 1.1508 mph = 1.853 kmph

To convert Kilometres per hour to Miles per hour .....multiply by 0.6214
To convert Miles per hour to Kilometres per hour ....multiply by 1.609
To convert Kilometres per hour to Knots per hour ....multiply by 0.5396
To convert Knots per hour to Kilometres per hour ....multiply by 1.853


Larger displacement sailboats can usually travel faster than smaller boats because hull speed depends on the length of the boat’s waterline and the volume of water displaced. Maximum speed is a function off:
In Knots =1.34 x (the square root of the waterline length of boat) in feet
In Knots = 2.43 x (the square root of the waterline length of boat) in metres
In km/h = 4.5 x (the square root of the waterline length of boat) in metres
See 'the three magic numbers for optimum sailing comfort and efficiency'.


Distance = Speed x Time
Speed = Distance ÷ Time
Time = Distance ÷ Speed

60 D ST
Distance in knots
Speed in nautical miles per hour
Time in minutes

Speed = (60 x Distance) ÷ Time
Distance = (Speed x Time) ÷ 60
Time = (60 x Distance) ÷ Speed


Horsepower to Kilowatts: x 0.7457
Kilowatts to Horsepower: x 1.341


Amps equals watts divided by volts External link.

Example how long can a 1 watt bulb run on a battery:
Watts = Volts x Amps
1 W = 12V x i, (i = 1 W / 12 V) i = .083 Amps

Then divide the number of Amp hours available in the battery bank to determine the number of hours that the load can operate.


Distance to the horizon in nautical miles = 1.17 x (square root of your eye height)
Distance at which an object becomes visible = 1.17 x (square root of your eye height) + 1.17 x (square root of the height of the object)


Atmospheric pressure at sea level = 14.7 psi
For each foot of water depth, pressure increases 0.445 psi
Pressure doubles every 33 feet

Example: Calculate pressure at a depth of 66’ 66’ x 0.445 psi / ft = 29.37 + 14.7 = 44.1 = 3 atmospheres For each 1,000 feet in altitude, pressure decreases 1 foot of head or 0.433 psi, so at 2,000 feet above sea level, pressure would be 14.7 – 2 x 0.433 = 13.83


Average at sea level: 29.92 inches = 1013.2 millibars (range 950 mb – 1035 mb) Inches of mercury x 33.86 = Millibars

Millibar ÷ 33.86 = Inches of mercury

With thanks to:
Michael Harpur, Yacht Obsession
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