This is a free online tool for converting the number of inches to pixels.
How many inches would you like to convert today?
You also need to know the density of pixels (Which is not the same as resolution).
A designer can set their own resolution (PPI - pixels per inches) but you can also read it in the image properties.
A printer can print different size pixels so it uses (DPI - dots per inches).
Density (PPI or DPI):
Include decimals but not fractions.
What Pixel Density should I use?
Some claim that the standard for web based design is 72 PPI or 96 PPI. I use 300 PPI for the web and printing (300 DPI).
GIMP, an image manipulation program, also shows 300 PPI as the standard for new images.
Learn more about pixel density here:
DPI to PPI Converter
PPI to DPI Converter
Typical Inches to Pixels Conversion Results
These are common results when you consider a 300 DPI pixel density: