Custom paper size looks like control until you try to hit a finished rectangle. Most tiled-poster workflows let you pick A4, Letter, or a custom sheet, then ask how many of those sheets should sit across the wall. The assembled height is whatever that grid happens to produce. A how-to that starts with rasterbator has to name that gap: paper choice describes each printed page, while the poster you hang is a different measurement.
Rasterbator puts both questions on the same setup screen as two radios. By N sheets wide asks for a grid and then calculates the finished size. Exact size asks for Width and Height when the poster needs to fit a measured space, then reports the paper plan underneath. The claim worth checking is simple. If a reader already knows the wall, frame, or board in centimetres, the sheet-count radio answers a question they did not ask.
- Sheet Count Answers The Wrong Size Question
- Score Both Radios Against A Finished Rectangle
- What Each Poster Size Radio Calculates First
- Where Sheet Count Approximation Breaks The Wall
- Exact Size Makes Paper Count A Consequence
- Enter Width And Height In One Unit
- Read The Sheet Grid After The Size
- Custom Paper Still Is Not The Poster
- Ten Millimetre Margins Protect Trim Marks
- When Exact Size Is The Wrong Radio
- Choose The Radio That Matches The Job
Sheet Count Answers The Wrong Size Question
A tutorial that says “make it four sheets wide” sounds complete. It is only complete if the reader wanted a stack of paper. It is incomplete if they wanted a 90 by 60 centimetre panel beside a desk, or a square that clears a light switch. Sheet count fixes one axis of the grid. The other axis, the margins, and the paper orientation still decide the real object.
That is why competing tools can offer custom paper and still miss the job. Changing the sheet from A4 to a slightly taller custom page changes every tile. It does not let the reader lock the assembled Width and Height first. The wall stays approximate until someone prints, tapes, and measures the result.
Write the target rectangle on a sticky note before opening the workspace. Paper = each sheet. Exact = the assembled wall. If those two lines get swapped, later advice about trim marks and page labels only documents a guess.
Score Both Radios Against A Finished Rectangle
Score the two radios, not two brands. One radio treats the grid as the input. The other treats the finished size as the input and lets the grid follow.
| Control | What You Type | What Gets Calculated |
| By N sheets wide | Sheet count in one direction | Height and finished size after paper, orientation, and margins |
| Exact size | Finished Width and Height | Sheet grid, page count, and cut plan for that rectangle |
The first row is honest when the wall is open-ended. The second row is the one that matches a measured space. If a how-to buries that split, readers will keep tuning paper size and wonder why the poster still overshoots the tape.
What Each Poster Size Radio Calculates First
By N sheets wide states its own logic: choose how many sheets wide, and the tool will calculate the height and finished size. Exact size states the opposite: enter the finished size when the poster needs to fit a measured space. Those two sentences belong in the article, not only in the interface. They tell a reader which number they are allowed to defend later.
Where Sheet Count Approximation Breaks The Wall
The break is visible as soon as the target has two hard sides. A 76 centimetre square is not “about four A4 sheets.” Four sheets across can land near that width, then produce a height the room cannot spare. When I placed the first export beside a taped 76 centimetre mark, the sheet-count plan looked fine until the second axis ran past the tape.
Exact Size Makes Paper Count A Consequence
Paper still matters. Set it first: A4 210 × 297 mm, US Letter 8.5 × 11 in, or another size from the paper list, plus Portrait, Landscape, or Auto (fewest sheets). Margins default to 10 mm. Then continue to poster size and switch to Exact size. The paper choice now describes each tile. The Width and Height fields describe the assembled result.
Units can be centimetres or inches. Keep the same unit that is on the sticky note. Mixing a centimetre wall with an inch field is a quiet way to invent a second poster. Keep image proportions stays available if the source and the rectangle disagree; that is a crop decision, not a substitute for entering both sides.
Enter Width And Height In One Unit
Type both sides. A single width with a guessed height puts you back in sheet-count thinking. Read the live summary after the numbers land. The workspace reports the finished size and the paper use together, for example 76.0 × 76.0 cm using 12 sheets of A4 in a 4 × 3 grid. If the first number pair does not match the sticky note, do not print. Change the fields, not the wall.
Read The Sheet Grid After The Size
This is where the rasterbator earns the how-to. The sheet grid is now an output. Page count can rise or fall when you switch A4 to Letter or Auto (fewest sheets) to Landscape, while the requested rectangle stays put. That is the difference readers keep missing when they only customize paper. Paper efficiency is useful. It is not the finished poster.
Open the Printed sheets tab before download. Corner pages show whether the trim marks and image content still fit within the conservative margin. If a needed edge already kisses the unprintable area, raise the margin or change paper. Do not hope the printer will recover a line that the tile never contained.
Custom Paper Still Is Not The Poster
Custom paper is a real control. It does not replace Exact size. A slightly taller sheet can reduce page count or change orientation. The assembled Width and Height still come from whichever poster-size radio is active. If that radio is still By N sheets wide, a custom sheet only moves the approximation.
Page margin is the other paper-side control people confuse with finished size. The 10 mm default is a conservative buffer for unknown home printers, not a claim that every engine needs 10 mm. Most documented hard margins sit lower. The extra space exists so trim marks and image edges survive feeding, duplex quirks, and Letter-versus-A4 differences. Shrinking the margin to save paper can clip those marks. It does not make the poster larger in the way Exact size does.
Ten Millimetre Margins Protect Trim Marks
Leave 10 mm unless a test page on the same printer, paper, and driver has already cleared a smaller value. A discarded first sheet is cheaper than an unreadable cut guide on page 12. If the corner ruler or trim mark is missing after that test, the driver scaled the PDF or the margin was too tight. Fix scale and margin before touching the rest of the stack. That hour of reprinting is almost always rework, not a paper-size problem.
When Exact Size Is The Wrong Radio
Sheet count still fits a wall with no hard rectangle: a garage that can absorb extra centimetres, a temporary display that only needs “large enough,” or a first look at how many pages a photo will consume. Exact size will not invent a missing measurement, and it will not stop Fit or Shrink in the print dialog from wrecking the geometry. Hardware can still clip marks if the margin is too small. Use Exact size when two sides are already known. Use sheet count when they are not.
Choose The Radio That Matches The Job
Rasterbator is worth the setup time when a how-to must produce a named rectangle on ordinary paper. Pick Exact size, enter both sides, then let the sheet grid follow. Keep sheet count for open walls and early page estimates.
Skip the tool if the job is one shop-printed sheet, or if nobody will print at Actual Size. The radios only help readers who will defend a physical measurement after the PDF leaves the browser.
The next article you write should start with the sticky note, not with a sheet count. If those two lines still agree after download, the paper plan did its job.
