1. See what kind of poster you need. If used on cans, cans come in several sizes, depending on what you need. It's best to ask where the poster is made. Buy a can first and then decide to fit the size of the can.

2. If you simply hang it on the wall, you have to look at the area you posted to calculate the size.

3. If it is a mobile phone, you should pay attention to this. On the one hand, you should pay attention to clarity and keep the file small. You can measure the size of the 5.5-inch mobile phone screen.

4. If it's a computer, it's best to set it to 1080P format and measure it yourself, or go to the website to measure other people's sizes. The error is not a big problem at all.