Listed on the maker's page · checked 2026-10-20

Blaze King King 40 wood stove

Blaze King publishes no heating area for the King 40; it gives 38,516 BTU/h (constant heat output on High). The firebox holds 4.35 cubic feet, #1 by size of the 20 stoves listed here, and particulate emissions are 1 g/h, 50% of the EPA's 2 g/h limit.

1Heating area No area published
2Output 38,516 BTU/h
3Firebox 4.35 cu ft
4Particulate 1 g/h

Specification	Blaze King King 40
Heating area	No area published
Output	38,516 BTU/h (constant heat output on High); low 10,392 BTU/h
Efficiency	81% (efficiency; the page does not say HHV or LHV)
Particulate emissions	1 g/h
Firebox	4.35 cu ft
Log length	Not published
Flue	8 in
Weight	Not published
Burn time	up to 40 hours on Low

Published output of the Blaze King King 40 and the four listed stoves closest to it. Makers define the figure differently (maximum, top of the EPA test range, or constant output on High); each stove's page says which. Bars to scale from zero.

What the King 40 heats

Without a published area, compare the output with the heat a house needs. Estimated loss on a 0°F night (from average-winter use):

Floor area	1970s house, Oregon	Pre-1950, North Dakota	Within 38,516 BTU/h?
1,000 sq ft	15,024	19,224	Both
1,500 sq ft	22,537	28,836	Both
2,000 sq ft	30,049	38,448	Both
2,500 sq ft	37,561	48,061	Median state only

These are estimates from average use, not a heat-loss calculation of a real house, and a stove heats the room it stands in first. The King 40 runs from 10,392 to 38,516 BTU/h, a 3.7-to-1 range, which helps in mild weather when a big stove would otherwise be turned down and smoulder.

Wood it burns in a winter

With its published 81% efficiency and a 1,500 sq ft example house, heating 1,500 sq ft (built in the 1970s) on generic 20 million Btu cords takes about 2.7 cords in Oregon and 4.7 cords in North Dakota. The maker quotes up to 40 hours on Low per load.

The species that burn best in any stove are the dense hardwoods Utah State rates excellent overall: osage-orange (30.5), black locust (28.3), white oak (27.9), apple (27), bur oak (26.3) million Btu per cord. Burn them dry; see how to season firewood.

Emissions and EPA rules

At 1 g/h the King 40 is 50% of the EPA's May 15, 2020 limit of 2 g/h and 40% of the 2.5 g/h limit for stoves certified on cord wood. The EPA rules guide explains the limits.

Similar stoves

Blaze King Ashford 30.2: 37,742 BTU/h, No area published
Blaze King Princess 32: 36,300 BTU/h, No area published
Woodstock Ideal Steel Hybrid 210: 43,263 BTU/h, Up to 2,200 sq ft
Blaze King Ashford 20.2: 32,776 BTU/h, No area published

Source: Blaze King, King 40 product page, checked 2026-10-20. Ratings are the maker's own; installation clearances and permits follow the installation manual and local code. See the methodology.