What the calculator actually solves
Hanging a row of pictures is three separate sums, and people usually get the second one wrong. First, how wide is the whole arrangement. Second, where does the first frame start so the row is centred. Third, how far above the floor does the hook go, which is not the same as the top of the frame.
The calculator does all three from canonical millimetres, so switching between inches and centimetres changes only the formatting. Nothing is rounded until it is displayed, which matters once you have five or six frames and small errors would otherwise accumulate across the row.
- Arrangement width = frames × frame width + (frames − 1) × gap
- Side margin = (wall width − arrangement width) ÷ 2
- Each left edge = margin + index × (frame width + gap)
- Hook height = frame bottom + frame height − measured hanger drop
Two ways to space a row
Hold the gap when you already know the spacing you want — most rows look right at 2 to 3 inches between frames — and read the side margins that fall out of it. This is the mode to use when the wall is generous and you simply want the row centred.
Hold the total width when the arrangement has to match something below it, such as a sofa, a sideboard, or a headboard. Enter the width you want the row to occupy and the calculator solves for the gap instead. If the frames alone already exceed that width, the gap comes back as zero and a warning appears rather than the tool silently overlapping frames.
Choosing a centre height
In a room you stand in, 57 to 60 inches above the floor is a common starting point for the centre of the arrangement. It is a convention, not a rule: it comes from average standing eye level in a gallery, and a dining room where everyone is seated or a hallway seen from below can justify something lower.
Above furniture, ignore the convention and work from the furniture instead. Leave 6 to 10 inches of clear wall above a sofa back, or 8 to 12 inches above a headboard, and let the centre height land wherever that puts it. Enter the resulting centre height here and the frame bottom and top edges are reported alongside it.
Why the hook is not at the top of the frame
The number that ruins most installs is the hanger drop. A sawtooth sits a few millimetres below the frame top; a wire under load can drop an inch or more; D-rings sit wherever they were screwed. The hook has to go at frame top minus that drop, and the only reliable way to know the drop is to measure it on the frame in front of you.
Hold the frame face down, pull the wire taut towards the top edge as if the frame were hanging, and measure straight down from the top of the frame to the highest point of the wire. For a sawtooth or D-ring, measure to the point the hook will actually engage. Enter that value and the hook height appears; leave it blank and the result stays an honest frame-edge plan.
- Sawtooth: measure to the notch that takes the hook
- Wire: measure with the wire pulled taut, not slack
- D-rings: measure to the ring centre, and note the side inset too
- Never assume a drop from the frame's packaging
Rows, grids, and when to stop using a calculator
A single row is the one arrangement where arithmetic is enough. Once you have two rows, mixed frame sizes, or an obstacle such as a light switch, a thermostat, or a television, the problem stops being a formula and becomes a fit problem: which positions are still legal given everything else on the wall.
That is what the full planner is for. It holds the same millimetre model, adds keep-clear zones for windows, doors, furniture, outlets and no-drill areas, checks every frame against the wall edges and against every other frame, and exports a coordinate table you can mark from. Use the calculator for a row; move to the planner for a wall.
Marking the wall from these numbers
Work from one datum, not from the previous frame. Measure and mark every left edge from the same left-hand corner, and every height from the same floor line. Measuring frame two from frame one, then frame three from frame two, accumulates every small error along the row, which is exactly how a level row ends up visibly sloping.
Check the floor and ceiling are not misleading you. Older floors are rarely level, so use a spirit level or a laser line for the horizontal datum rather than measuring up from the skirting board at each position. Then verify wall construction and pick a fastener rated for the frame weight before anything goes in.
What this tool does not decide for you
The calculator makes no claim about whether a fixing will hold. Frame weight, wall construction, anchor rating, and hardware condition are all outside the arithmetic, and drywall, plaster, and masonry all behave differently. Read the rating printed on the fixing you are actually using and choose accordingly.
It also gives no structural, electrical, or building-code advice. Before drilling, check for cables and pipes behind the surface, and treat anything above a bed or a seat as a safety decision rather than a design one.