Line 44 is the income tax calculated based on your taxable income on line 43.
To verify the amount, if your income is less than $100,000, take the amount on line 43 and refer to the income tax tables in the form 1040 instructions below.
If your income is above $100k, you must use the tax computation worksheet (also in the instructions).
You can find this information and the tables to check your tax, in the Form 1040 Instructions (page 41), here: https://www.irs.gov/pub/irs-pdf/i1040gi.pdf