How to calculate capital gain tax?

If this is a business asset then you will have to use the 1040 tax form 4797 to report the transaction on.

You will use the information that is on the 1099-B to report the transaction on your 1040 tax form.

If this is personal property (non-business) and you have owned it for more than one year and it is sold at a gain. You will have a long term capital gain (LTCG) that will be taxed at the 0% to 15% maximum capital gain tax rate.

The transaction will be reported on the schedule D of the 1040 tax form.

When you complete the schedule D all the way through line by line the LTCG will be taxed at the 0% to 15% maximum capital gain rate. You will have to complete the schedule D worksheet on page 10 of the schedule D instruction book all the way through line 36 as that will be where the tax numbers will come from to go on line 44 of your tax return.

For forms and instruction go to IRS gov website and use the search box for schedule D and you will find the instructions and form that you would use for this purpose.