Gallery Wall Spacing: Measure Gaps and Layout Size
A useful gallery wall spacing guide should let you calculate the finished layout before anything reaches the wall. For most home poster arrangements, start with a 5-7 cm edge-to-edge gap, then calculate the group width and height from the actual outside dimensions of every print or frame. The gap is only one number; the full footprint tells you whether the composition fits.
This page uses centimetres and current A4/A3 print dimensions. Treat every suggested gap as a starting point rather than a rule. Your frame moulding, viewing distance, furniture and usable wall boundary still decide the final result.
The quick gallery wall spacing answer
| What you are arranging | Starting gap | What to check |
|---|---|---|
| A5 or small unframed prints | 3-5 cm | Can each image still be read at arm's length? |
| A4/A3 prints or medium frames | 5-7 cm | Does the set read as one group from the normal viewing point? |
| Large frames | 7-10 cm | Has the wider gap pushed the complete group beyond the available wall? |
| Mixed sizes | Choose one base gap | Measure edge to edge, not centre to centre. |
The 5-7 cm middle range is close to the 2-3 inch starting point in Blick's gallery-wall planning guide. It is useful as a first mock-up, not evidence that every wall needs the same distance. Lay the pieces out, view them from where you enter or sit, and change the gap in 1 cm steps if the group feels either crowded or disconnected.
Measure print edges or frame edges-never mix them
Unframed print: measure from one paper edge to the other. An A4 sheet is 21 × 29.7 cm; an A3 sheet is 29.7 × 42 cm. ISO 216 is the underlying paper-size reference, and the ISO overview confirms that it defines the A-series trimmed sizes.
Framed print: measure the finished frame from its outermost left edge to outermost right edge, then top to bottom. A frame described as “A4” is made to hold A4 artwork; that label does not tell you its outside wall footprint. Moulding and mats add size. The Frame Destination measurement guide makes the same distinction between artwork size and the frame's outside dimension.
- Inner gap
- The visible wall between two neighbouring print or frame edges.
- Outer margin
- The wall left between the complete gallery and a wall edge, window, shelf, switch or furniture boundary.
- Mat border
- The card border inside a frame. It changes the visible artwork area, not the gap on the wall.
- Hook position
- The hardware coordinate behind a frame. It is calculated after the visual layout, not used as the visual gap.
If one framed A4 measures 25 × 34 cm outside and another measures 28 × 37 cm, use 25 × 34 and 28 × 37 in the wall calculation. Using 21 × 29.7 for both would make the planned group too small.
Calculate the total gallery wall size
For a regular grid of equal-size pieces:
Total width = (columns × outside width) + ((columns - 1) × horizontal gap)
Total height = (rows × outside height) + ((rows - 1) × vertical gap)
Horizontal and vertical gaps may be different, but decide both before calculating. Outer margins are not included in these formulas. Add them afterwards when testing the group against the usable wall.
For a centred layout, the remaining side margin is:
Margin on each side = (usable wall width - total gallery width) ÷ 2
“Usable wall” means the section you are prepared to occupy, not automatically the full room wall. A door swing, curtain stack, switchboard or wardrobe opening can reduce it.
Three worked A4 and A3 examples
Example 1: six A4 prints in a 3 × 2 grid
Use six unframed A4 portrait prints, three columns, two rows and 5 cm gaps in both directions.
On a 120 cm usable wall, centred side margins would be (120 - 73) ÷ 2 = 23.5 cm each. If you add frames, repeat the calculation with the outside frame width and height.
Example 2: two framed A3 prints in one row
Suppose each A3 print is in a frame measuring 35 × 47 cm outside. Place the frames in one row with a 7 cm edge gap.
35 × 47
35 × 47
Measure your own frames; 35 × 47 cm is an example, not a promised Art Theory frame dimension. This is the calculation to use above a desk or narrow console where a few centimetres decide whether the pair fits.
Example 3: one A3 beside two stacked A4 prints
Place one unframed A3 portrait beside a column of two unframed A4 landscape prints. Use 4 cm between the two columns and 4 cm between the stacked A4s.
29.7 × 42
The A3 column is 4 cm shorter than the A4 stack, so centre it vertically to leave 2 cm above and below. This is the difference between measuring the bounding rectangle and merely adding all print heights together.
Adjust grids, columns and organic layouts
Grid
Measure the outside width and height of every piece. Equal paper sizes do not guarantee equal finished frames. Build the first row and first column from paper templates, check both with a level, then use those edges as references for the remaining pieces.
Vertical column
Add every outside height and the gaps between them. A column of three A4 portraits with 5 cm gaps is 29.7 + 5 + 29.7 + 5 + 29.7 = 99.1 cm high. Centre that complete 99.1 cm group inside the usable strip beside a desk or door; do not centre each print separately against the whole wall.
Organic gallery
Draw an imaginary outer rectangle and choose one base gap. Start with the largest piece, then place neighbours at the chosen edge distance. With angled or irregular frames, measure the shortest edge-to-edge point so two corners do not accidentally touch while the opposite sides appear far apart.
Organic does not mean every void must be identical. It means a deliberate base rhythm, plus occasional larger spaces where the composition needs them. For colour, subject and frame decisions beyond the measurements, use the mixed-art gallery wall guide.
Separate inner gaps from furniture and wall-edge margins
Calculate the art group first, then place that rectangle in the room. Measure the clear wall above a headboard or desk and subtract the gallery footprint. What remains is available for outer margins; it is not another inner gap.
For example, a 73 cm-wide A4 grid centred above a 150 cm headboard leaves 38.5 cm from each headboard edge to the gallery edge. That number describes the relationship to the furniture. The 5 cm spaces inside the grid still remain unchanged.
- Mark curtain movement and door or wardrobe swing before choosing the usable boundary.
- Keep switches, sockets, shelves and wall lamps outside the paper template unless the design intentionally works around them.
- Check the complete rectangle from the doorway and the normal seated position.
- When the wall is narrow, calculate a column rather than compressing a wide grid.
Use the bedroom poster-wall layout guide for bed-specific arrangements and the narrow-wall gallery guide when doorways or tight corners define the available strip.
Fix uneven gallery wall spacing
One gap looks wider: measure between the visible outside edges, not the hooks. If the frames differ in width, equal centre-to-centre spacing produces unequal visible gaps.
The last column drifts: recheck the first reference column with a level. Small errors compound across a grid. Move paper templates before moving mounted pieces.
The group is too wide: reducing every gap by 1 cm saves 2 cm across a three-column layout because there are two horizontal gaps, not three. If that is not enough, change the arrangement or remove a piece rather than erasing the outer margin.
A mixed layout has an empty pocket: align one edge or baseline with a neighbour. Do not solve every pocket by adding another small print; first check whether shifting an existing column closes it.
The frame calculation is wrong: measure each finished outside dimension again. Packaging size, artwork size, mat opening and outside frame size answer different questions.
Before mounting, cut paper templates to the actual outside dimensions and label each one. Tape the full composition to the wall, then verify gaps with a ruler. The multiple-poster hanging guide covers the next step; the poster size guide helps if the print sizes themselves are still undecided.
Gallery wall spacing questions
How much space should be between gallery wall pictures?
Start with 5-7 cm for many A4/A3 or medium-frame arrangements, then check the group from its normal viewing position. Small unframed prints may work at 3-5 cm; large frames may need more. Recalculate the total footprint whenever the gap changes.
Do you measure between prints or frames?
Measure between the outermost visible edges of whatever is going on the wall. Use paper edges for unframed prints and outside frame edges for framed art. Never calculate a framed gallery using only the paper dimensions.
How do you calculate gallery wall width?
For equal pieces in a row, multiply the outside width by the number of columns, then add one fewer gap than the number of columns. Three 21 cm-wide A4 portraits with 5 cm gaps measure (3 × 21) + (2 × 5) = 73 cm.
Should outer margins equal the gaps between pictures?
No. Inner gaps organise the pieces inside the composition; outer margins position the complete composition against furniture and room edges. Calculate and judge them separately.
Write down five things before you hang: every outside width, every outside height, columns, rows and the chosen gap. Calculate the footprint, tape that rectangle to the wall, and only then choose the mounting points. That gallery wall spacing plan is ready when its inner gaps and outer margins both work on the real wall. Browse Single Posters if you need specific A-sizes to complete it.