BTU calculator

[Bill Edwards(2)]

With all these posts about heaters (which I'll confess to not following very closely) does anyone have a good BTU calculator?

Most that I find talk about square feet, which doesn't seem very accurate to me.

What if your ceilings are high?

[Todd Crawford]

http://www.heatershop.com/btu_calculator.htm

[Bill Edwards(2)]

Thank you, Todd

[Mark Bolton]

Something to remember with many of these calculators on the web is they can way overshoot and often dont account for doors and windows. A very good rule of thumb I learned about 20 years ago and use to this day is:

For an average space in an average location with R13 walls, and R30 ceilings is to calculate your cubic footage and multiply x 4, then add 500 for for each door and window. In an average heating climate it takes about 4BTU per cubic foot of air with no windows or doors.

Example (a small outbuilding we just did for a customer) 12x20 w/7.5' ceilings. 12x20x7.5x4+500(door)+500(window)+500(window)=8700 BTU. This would be about 2500watts of electric (what this customer wanted). We used two 4' baseboard units. Super toasty here with 10 degree nights.

Mark