A gallery wall layout planner that shows its work.

Start by entering the wall you actually have. Width and height are stored in millimetres, so switching the display between inches and centimetres changes formatting and input conversion only — it never transforms the geometry underneath. The canvas then holds the wall's real aspect ratio, which is why a 120 by 40 inch hallway strip looks like a hallway strip rather than a square.

Add frames either by picking a standard size, entering custom dimensions, or applying one of the five dimensioned templates. Every frame is stored as a left edge, a bottom edge, a width, and a height, measured from the wall's bottom-left corner. That bottom-left origin is the point of the whole tool: the vertical number you read is a real height above the floor, not a position on a screen.

Most layout tools will happily let two frames overlap or let a frame run off the edge of the wall. This one treats those as errors and says so. Every frame is checked against all four wall edges and against every other frame, and any overlap is reported as a collision rather than quietly recorded as a zero gap.

You can also add keep-clear zones for the things that actually constrain a wall: a window, a door swing, the top of a sofa, an outlet, or an area you simply cannot drill. The constrained auto-fit respects those zones and any frames you have locked, and it tells you when a piece could not be placed instead of putting it somewhere invalid.

Horizontal gaps are only measured between frames whose vertical projections overlap by at least 45 percent of the shorter frame. Vertical gaps use the same rule across horizontal projections. That means the reported gap is the gap between actual neighbours, not the distance between two frames that happen to be adjacent in a sorted list but sit on different rows.

Coverage is the arrangement's bounding-box width divided by wall width, and the equivalent for height. Summing frame widths would double-count anything stacked in rows and would tell you a two-row grid covers more wall than it does. The arrangement centre reported from the floor is the midpoint of that same bounding box.

A rectangle on a wall is not a nail. Frame-edge coordinates need nothing but the wall and the frames, so they are always available. A hook or drill position additionally needs the hardware model and its measured offsets, which only you can supply from the frame in your hands.

Choose centred sawtooth, centred wire, or a D-ring pair and enter the measured drop from the frame's top edge — plus the side inset for D-rings. Until every frame has valid offsets, the export is deliberately labelled a frame-edge layout plan rather than a hardware mark map. A wire point stays labelled estimated unless you confirm the drop was measured under load, because a slack wire measurement is the single most common cause of a picture hanging low.

Artwork images you attach are read by the browser into the current project. There is no upload endpoint, no account, no email capture, and no cloud project store in this release. Save local writes the project to this browser's storage; Project file downloads portable JSON you can move between devices or keep as a backup.

The print and PDF install sheet includes 4-inch and 10-centimetre calibration bars, because printer margins, paper size, and browser scaling can all change physical scale. Print at 100 percent or Actual size, check the bars against a tape measure, and only then trust anything measured off the paper.