THE NUMBERS, EXPLAINED
How to use this calculator.
An unfolded geometric cover spread using your supplied spine, bleed and any extra hinge allowance. Hinge allowance adds width rather than taking space from the cover panel. Read positions from the left file edge. Use zero hinges unless your printer specifies this extra geometry; its template overrides this estimate.
Start with your inputs
Enter trim cover width (mm), trim cover height (mm), supplied spine width (mm), outer bleed on each edge (mm), additional hinge allowance on each side of spine (mm). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Trim cover width (mm) | 150 |
| Trim cover height (mm) | 210 |
| Supplied spine width (mm) | 12 |
| Outer bleed on each edge (mm) | 3 |
| Additional hinge allowance on EACH side of spine (mm) | 0 |
A worked example
With the example inputs above, flat spread width (mm) is 318. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Flat spread width (mm) | 318 |
| Flat spread height (mm) | 216 |
| Back panel end (mm) | 153 |
| Spine left (mm) | 153 |
| Spine right (mm) | 165 |
| Front panel start (mm) | 165 |
How this is calculated
Flat spread width (mm)
Two cover widths + spine + two hinges + two outer bleeds.
Flat spread height (mm)
Cover height + two outer bleeds.
Back panel end (mm)
Left bleed + back cover width.
Spine left (mm)
Back panel end + hinge allowance.
Spine right (mm)
Spine left + spine width.
Front panel start (mm)
Spine right + hinge allowance.
Symbols and units
- a
- Trim cover width (mm)
- b
- Trim cover height (mm)
- c
- Supplied spine width (mm)
- d
- Outer bleed on each edge (mm)
- e
- Additional hinge allowance on EACH side of spine (mm)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions and limits
An unfolded geometric cover spread using your supplied spine, bleed and any extra hinge allowance. Hinge allowance adds width rather than taking space from the cover panel. Read positions from the left file edge. Use zero hinges unless your printer specifies this extra geometry; its template overrides this estimate.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Flat spread width (mm); Flat spread height (mm); Back panel end (mm); Spine left (mm); Spine right (mm); Front panel start (mm). The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: An unfolded geometric cover spread using your supplied spine, bleed and any extra hinge allowance. Hinge allowance adds width rather than taking space from the cover panel. Read positions from the left file edge. Use zero hinges unless your printer specifies this extra geometry; its template overrides this estimate.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Further reading
IngramSpark: use printer-specific cover templates ↗
Background reading; this does not imply endorsement or independent review of SumFizz.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
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