When you insert an image to the header, the size of the image may be too big, and in this case, you need to resize it.
1. Click View > Page Layout to display the header, see screenshot:
2. Go to click on the header to display the Design tab. See screenshot:
3. Click Format Picture under Design tab, and then you can resize the Height and Width as you need under Size tab in the Format Picture dialog. See screenshot:
4. Click OK. Then the header image has been resized. See screenshot:
Supercharge Your Excel Skills with Kutools for Excel, and Experience Efficiency Like Never Before. Kutools for Excel Offers Over 300 Advanced Features to Boost Productivity and Save Time. Click Here to Get The Feature You Need The Most...