Mailer Size Calculator
Estimate a practical starting size for a flat custom mailer from the dimensions of your packed product. Measure the product exactly as it will be packed, then choose whether you want any extra room beyond the minimum recommendation.
How the calculation works
The calculator starts with the packed product width, length and finished depth / height. It allows for the way a flat mailer wraps around that depth, then adds a small practical clearance and rounds the result upward to a production-friendly 5 mm increment.
The quoted mailer body size excludes the adhesive flap. Single-adhesive flap length is shown separately, and double-adhesive mailers use a larger flap.
What the result does not tell you
This is a recommended starting size, not final manufacturing approval. Product shape, compressibility, loading method and how tightly you want the mailer to sit can affect the best finished size.
Flexible packaging can vary slightly during manufacture. For an uncertain or important custom size, check the fit with a physical sample or simple mock-up before production.
Frequently asked questions
Measure the product exactly as it will be packed. Record the finished width, length and maximum depth or height, including any inner packaging that will sit inside the mailer.
No. The recommended width and length are the usable mailer body dimensions. The closure flap is shown separately.
Yes. The calculator starts at Zero Pack’s minimum recommended clearance. Use the additional-room control if you want a looser fit or need more handling space.
Use the result as a starting point for your quote and specification. For custom production, especially where the fit is close, confirm the final dimensions with a sample or mock-up before manufacture.