Oct 26, 2023 · Here are my general recommendations for sheet metal thickness based on stove size: Small stoves: 22 gauge stainless or 0.25 inch mild steel. Medium stoves: 20 gauge stainless or 0.25-0.375 inch mild steel. Large stoves: 18 gauge stainless or 0.5+ inch mild steel. XL stoves: 16 gauge stainless or 0.75+ inch cast iron.