Depends on manufacturer recommendation; read the box or brochure for the furnaces you are considering.
I would say a 40,000 BTU furnace could big enough to heat a 400 SQ ft house, but where have you found a 400 SQ Ft house?
2500sq ft in northern climate
80000
The size of the furnace needed for a 2,200 sq ft house in New Jersey typically ranges between 70,000 to 90,000 BTUs, depending on various factors such as insulation, ceiling height, and local climate conditions. A Manual J calculation, which considers these factors, is recommended for a more accurate assessment. Additionally, consulting with a local HVAC professional can help ensure you select the right furnace size for optimal efficiency and comfort.
I strongly urge you to call a pro HVAC company and have them perform a manual J load calculation . However for years ,typically 75,000 to 100,000 btu furnaces in the south USA were the norm. Tom H. HVAC proffesional, New Orleans
For an 800 sq ft house in Ohio, a furnace with an output of about 40,000 to 60,000 BTUs is typically recommended, depending on factors such as insulation quality, ceiling height, and local climate. It's important to perform a heat load calculation to account for these variables for optimal efficiency. Consulting with a local HVAC professional can ensure you choose the right size for your specific needs.
rooms are 325 sq ft and suites are 625 sq ft
No, despite that people will understand what you have written. But still 3 ft sq is not same as 3 sq ft.
21 ft * 10 ft = 210 sq ft = 19.51 sq metres.
A 60,000 BTU/hr. furnace will heat a 1400 square foot house. However, the average daily temperature, house insulation and other factors will have to be considered before making a final decision.
You cannot accurately determine what size furnace is required based on the total square feet of a given space or structure. To accurately determine how much heat is required to heat your, you would need to have a Manual J Heat Load Calculation performed.