How to Measure and Cut Perfect Letterbox Box Templates
DIY guide to measuring, designing, and cutting letterbox box templates for prototyping and small runs.
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Quick answer
Start with your product dimensions, add wall thickness and fold allowances, draw the net on card stock, score the fold lines, cut, and assemble. Use 300-400gsm card for prototyping. The critical measurement is total thickness: product + two box wall thicknesses must stay under 25mm. Make 2-3 prototypes and test-pack before finalising. For production, send your template to a manufacturer who will create a professional die.
Measuring correctly
Measurement steps0 / 5 checked
Creating the template
Draw the box net (flat layout) on card, marking fold lines with dashed lines and cut lines with solid lines. Include tabs for gluing. Score all fold lines with a bone folder or empty pen before folding. A clean score line makes the difference between a crisp fold and a messy one.
A scored line folds cleanly and accurately. An unscored fold is imprecise and can crack the board.
A template is only validated when the product fits perfectly inside.
Prototyping is about fit and dimensions, not finish. Use any card stock you have.
Ready for production: find a supplier or sizing guide.
Testing your template
Pack the prototype with your product and test it through an actual letterbox. Check for snug fit, easy insertion and removal of the product, clean fold lines, and total packed thickness under 25mm. Make at least 3 prototypes to refine the design before approaching a manufacturer.
Custom letterbox boxes
Send your template to ProcuraPack for professional production in any quantity.
Browse letterbox boxesFrequently asked questions
Measure product, add clearance and wall thickness, draw the net, score fold lines, cut, and assemble.
300-400gsm card stock for initial prototypes. Your manufacturer will use corrugated board for production.
Total packed thickness must stay under 25mm (Royal Mail) and under 38mm (letterbox opening). Test physically.
At least 3 to refine dimensions before sending to a manufacturer.
Yes, send your validated template and they will create a professional die for production.
Part of our guide
Product Guide: Letterbox Boxes
Expert guides on letterbox packaging, from sizing and Royal Mail rules to branding and sustainability.
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