Use the same buckets, weigh a bunch of them when filled, average that weight. Now just count the buckets you use and multiply by your average.
Then with Excel, you can do some cool stuff, this is what I got from the data, there's more I did, such as auto-figuring when I'll run out of coal,
to the DAY, based on current usage.
I used 6,084 pounds over 143 days.
Average 42.5 lbs/day
Cost = $4.79/day (@ $0.1125/lb)
Heating results above from the following date range: 10/27/07 thru 3/18/08.
Stove: Hitzer, 30/95, double wall, duratech pipe.
Coal: Anthracite, pea size
Supplier: Dennis Coal
This is about a 1500 sq ft home, ranch style, in Central Square, NY.
In case you're wondering, this is me: http://www.iRecoverData.com
That explains the rather analytical answer!