Why is my Federal Tax liability higher than if I calculate by hand using tax tables ?

Look at your tax return, Form 1040, Lines 16 thru 24 to see your total tax liability.

You can view your Form 1040 plus Schedules 1, 2 and 3 at any time using the online editions. Click on Tax Tools on the left side of the online program screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.

Your tax liability is made up of a lot of elements.  The tax tables assume that your entire income is regular income taxed at your regular income tax rate.  It does not add in self-employment tax or the tax rates for capital gains or excess medicare or AMT.  

As @DoninGA says above the elements that make up your tax liability are available to use using the methods detailed above.

@scdoody