In principle it's simple enough but it depends on how you are billed and I
guess this is different country by country so for the UK if this helps:-

m3 gas * 1.02264 * 39.6 / 3.6 will give killowatts used so multiply by cost
per Killowat to get your bill.

However there's another complication. 39.6 is the calorific value of the gas
and this will vary month on month. Also you may find you are charged a higher
rate for the first x killowatts and a lower rate for subsequent usage.

Electricity is considerably simpler in that you are billed in Kw so a simple
formula:-

currenet meter reading-previous meter reading * cost per kw= bill ammount

Hope this helps!!

Mike

"grimwau" wrote:

I would like to be able to input my gas and electricity readings each month
and also the cost of each unit and/or therm to be able to compare month to
month/year to year costs.