Grid Overlay
Put a grid on a picture · set the line weight · save it
Image
Grid
Lines
Thickness is in pixels of the original image, so what you save matches what you see.
Save
Drop an image here
Or choose a file from the panel. Everything runs in this tab — the picture never leaves your device.
Finished image
On iPhone, press and hold the picture below and choose Save to Photos. On a computer, right-click it and choose Save image as…