Measure width, depth, and height
Start with the closed appliance dimensions: width from side to side, depth from front to back, and height from counter to top. Compare those numbers with the actual clear section of counter, not the total length of the countertop. Account for backsplashes, outlet covers, cabinet trim, and other appliances that reduce usable space.
Depth is often the overlooked measurement. A deep air fryer can extend far enough forward to crowd a work area even when its width seems manageable. For oven-style models, include the handle in the closed depth. For basket models, make sure the body does not sit so close to the counter edge that pulling the basket out feels awkward or unstable.
