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Math

Segment Addition Postulate Calculator

Solve AB + BC = AC for the missing segment.

Enter your values

Results update instantly as you type — no submit needed.

Results
Solved AC
12
AB
7
BC
5
AC
12
Check
AB + BC = AC ✓

Working

  1. 17 + 5 = 12

Quick answer

The segment addition postulate says that if B is between A and C, then AB + BC = AC.

AB + BC = AC

At a glance

What it doesSolve AB + BC = AC for the missing segment.
CategoryMath
Inputs neededSolve for, AB, BC, AC
Main outputSolved AC
FormulaAB + BC = AC
CostFree — no sign-up, no download

How to use the Segment Addition Postulate Calculator

  1. 1Choose which segment is unknown.
  2. 2Type the two lengths you know.
  3. 3Read the missing length and the consistency check.

Inputs explained

Solve for
Choose one of: AC (whole), AB, BC.
AB
Enter the ab you are working with.
BC
Enter the bc you are working with.
AC
Enter the ac you are working with.

Worked example

Using the values the calculator loads with:

Inputs

  • Solve forAC (whole)
  • AB7
  • BC5
  • AC12

Results

  • Solved AC12
  • AB7
  • BC5
  • AC12
  • CheckAB + BC = AC ✓
  1. 7 + 5 = 12

Frequently asked questions

What is the segment addition postulate?

If point B lies on segment AC between A and C, the two shorter pieces add to the whole: AB + BC = AC.

Can AB be longer than AC?

No — the whole segment AC is always the largest, so a negative result means the labels are swapped.

Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.