>Hi everybody,
>
>I just spent about 15 minutes googling and could not find simple formulas I need to implement for conversions of kg into pounds or stones and pounds, pounds into the other 2 and stone and pounds into the other two.
>
>Here is what I started to write but I can not find the formulas to use:
>
>

> $scope.updateWeight = function(weight1, weight2, units)
>            {
>
>                switch (units) {
>                    case 'kg':
>                        $scope.currentGuest.weightG = weight1 * 1000;
>                        $scope.currentGuest.weight = Math.round(weight1 * 2.20462); // weight in pounds
>                        $scope.currentGuest.weightStone = Math.round(weight1 * 0.15747); // weight in stones
>                        $scope.currentGuest.weigthLbs = // remainder for stones/pounds
>                        break;
>                    case 'lbs':
>                        
>                        break;
>
>                    case 'stones': // stones and pounds
>                        break;
>                }
>            }

Please note that the kilogram is technically a unit of MASS, not of weight. (A weight is a force, and therefore measured in newton.) Pound may be used both for mass and for weight.

The definition of "pounds", unfortunately, varies by country. This is one of several reasons to prefer SI.

To convert between lots of different units of the same type (for example, different mass units), I would suggest you store the equivalent of each unit in some standard - I suggest SI units. For example:

kg = 1 kg
gram = 0.001 kg
pound (Avoirdupois) = 0.453592 kg
pound (Germany) = 0.5 kg
ton = 1000 kg (also known as "metric ton")
ton (US) = 907.2 kg
short ton (US) = 1016 kg
solar mass = 1.988e30 kg (often used for comparisons in astronomy)

Now, to convert, say, from "ton" to "ton (US)", you would look both up in a table, check that they both convert to the same base units, in this case kg (it makes no sense to convert kilogram to meters, or square meters to meters, though this is a frequent question in online forums...) and then just divide one value by the other.

Similarly, you would store different length units in terms of meters, different area units in terms of square meters, etc.