How to convert pixels to inches
Divide each pixel dimension by the intended pixels per inch. A 3,600 × 2,400 px image at 300 PPI becomes 12 × 8 inches. At 150 PPI, those same pixels cover 24 × 16 inches.
What result should you use?
300 PPI is a common high-detail target for prints viewed closely. Larger work viewed from farther away may use a lower density. Your printer’s specification takes priority, and focus, compression, sharpening, paper and the printing process also affect the result.
Does changing PPI add pixels?
No. If resampling is off, changing the PPI metadata changes the intended physical size, while the pixel dimensions stay fixed.