What does TT mean when it tells me my "Blended Tax Rate"?

The Blended tax rate is calculated under Federal / Federal Review.   
 

To access it, all questions must be answered in the Federal Review. 

At the end of the questions. Look at the bottom of the screen 

It will say Get a detailed view of your numbers.

The Blended Tax rate is: 

• Tax liability (Including SE tax, capital gain and special taxes), 
•  Divided by 
• Taxable income (Total income minus deductions, but before credits). 
• (All line numbers are on form 1040). 
   

The Effective Tax rate is your:

• Total income (line 9) 
• Deductions (Line 12) This is Itemized or Standard 
• Taxable Income (Line 9 – Line 12) 
• Blended Tax Rate (Tax Liability [below] / Taxable Income [above]) 
• Tax Liability (Line 16 + Line 23) 
• Taxes Paid (line 25d) 
  Credits (Line 21) 
  Total Tax Paid (Line 21 + Line 25d) 
  Refund/Due (Line 34 or Line 37) 

Effective tax rate doesn't consider SE tax and any penalties, and blended tax rate does. Blended tax rate is a confusing and unnecessary term to be using in TT, and gets everybody all upset. 

You can compute it yourself with a calculator.

Effective tax rate is something Turbo Tax uses to help you see where you stand; to see which W-2 may be deficient in withholding the correct amount of Federal tax, etc. 

It should be the tax divided by the total income, not the AGI. It is a number without any real value other than just to let you know when you earn $1, about x% is taxed.

For more effective information see: 

• TaxCaster tax calculator
• Tax bracket calculator

It is an accounting calculation that means nothing to you and not worth trying to understand.   I wish TurboTax would just get rid of it.