Perspective tools, all of them.
Free online perspective tools for artists: interactive grids you can rotate, set by lens and export as a transparent layer, plus tools that fix, warp and analyse the perspective of photos. Everything runs in your browser and nothing you make leaves your device.
Which perspective tool do you need?
To draw something. Start with a grid. The 1-point grid is for rooms, corridors and roads seen straight on; the 2-point grid covers most buildings, furniture and vehicles; the 3-point grid is for looking up at a tower or down into a street; the curvilinear grid handles fisheye and 360° views that linear perspective cannot. Every grid rotates like a camera, reads out the lens in millimetres, and exports as a transparent PNG or SVG you can paste into Procreate, Photoshop, Clip Studio or Krita. The box generator adds real-size boxes, cylinders and figures to any of them.
To fix or reshape a photo. Perspective correction straightens leaning buildings, whiteboards and scanned pages; perspective warp puts a flat image onto a wall, screen or box; change image perspective tilts and turns a picture in 3D with a real camera field of view. All three run at full resolution on your device and nothing is uploaded.
To analyse a reference. The vanishing point finder reads the horizon, vanishing points, lens and tilt from a photo and opens the matching grid, so a drawing can sit inside a photographed scene. For the numbers behind all of this, the perspective calculators convert lenses, figure heights, horizons and vanishing-point spacing; for paper, the printable templates are the same grids sized for A4, A3 and Letter.
What makes these tools different
Most online perspective tools let you drag vanishing points around a canvas. These start from a camera: eye height, rotation, tilt and focal length. That is why a 24 mm grid here looks like a 24 mm photograph, why the horizon moves when you tilt, and why the export is a true vector SVG rather than a screenshot. Not sure which grid you need? Read 1-point vs 2-point vs 3-point perspective, or the guide to perspective tools if you are looking for the tool inside Photoshop, Illustrator or Clip Studio.