How several btu furnace do I obligation for a 1000 square foot house? looking to replace my existing furnace with a newer elevated effiecentcy furnace...

looking to replace my existing furnace with a newer elevated effiecentcy furnace but not sure how many BTUS I call for and not sure if I can trust a company not to sell me something difficult than I need.
Self-building stipulation lend a hand?
Answers:    I am a heat contractor in minnesota (very cold) and would single put a 40,000 btu furnace in that size home if it be newer construction with around 8' ceiling and decent window. If you have a crypt under the 1000 sq. ft. later you would want around 60,000 btu. Furnaces do come that small so don't listen to others who say they don't. Hope this help.
I a short time ago have a pipe...
80,000 BTU FURANCE-WILL DO