Midpoint Formula

The midpoint formula finds the coordinates of the point halfway between two endpoints on a line, given their x and y coordinates.

M=(x1+x22,;y1+y22)M = \left(\frac{x_1 + x_2}{2}, ; \frac{y_1 + y_2}{2}\right)

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What each symbol means

What Midpoint Formula takes
MM
x1x_1
y1y_1
x2x_2
y2y_2
Midpoint Formula
SymbolMeaning
MMThe midpoint—the single point that lies exactly halfway between the two endpoints, with both x and y coordinates equal to the averages of the original points.
x1x_1The x-coordinate (horizontal position) of the first endpoint; if you swap it with x₂ or treat it as a y-coordinate, your midpoint will shift horizontally to the wrong location.
y1y_1The y-coordinate (vertical position) of the first endpoint; confusing it with x₁ or using y₂ twice instead will place your midpoint at an incorrect vertical position.
x2x_2The x-coordinate (horizontal position) of the second endpoint; it pairs with x₁ in the averaging process, and the order does not matter since addition is commutative.
y2y_2The y-coordinate (vertical position) of the second endpoint; forgetting to include it or duplicating y₁ will cause you to miss the correct vertical position of the midpoint.

When to use it

Use this formula when you need to locate the exact center point between two known coordinates or positions.

Level

Usually taught in: Geometry · Appears on: SAT, ACT

Worked examples

1. Find the midpoint with small positive integers

Problem

Find the midpoint between the points (2,3)(2, 3) and (8,7)(8, 7).
  1. M=(2+82,3+72)M = \left(\frac{2 + 8}{2}, \frac{3 + 7}{2}\right)

    Substitute the coordinates into the midpoint formula with (x1,y1)=(2,3)(x_1, y_1) = (2, 3) and (x2,y2)=(8,7)(x_2, y_2) = (8, 7).

  2. M=(102,102)M = \left(\frac{10}{2}, \frac{10}{2}\right)

    Add the x-coordinates: 2+8=102 + 8 = 10, and add the y-coordinates: 3+7=103 + 7 = 10.

  3. M=(5,5)M = (5, 5)

    Divide each sum by 2: 102=5\frac{10}{2} = 5 for both the x and y coordinates.

Answer: (5,5)(5, 5)

This straightforward example uses the formula directly by substituting the given coordinates, adding them, and dividing by 2. Both sums divide evenly, yielding integer results with no rounding needed.

2. Find the midpoint with negative coordinates and fractional results

Problem

Find the midpoint between (3,5)(-3, 5) and (4,2)(4, -2).
  1. M=(3+42,5+(2)2)M = \left(\frac{-3 + 4}{2}, \frac{5 + (-2)}{2}\right)

    Substitute the coordinates, being careful with the negative signs: (x1,y1)=(3,5)(x_1, y_1) = (-3, 5) and (x2,y2)=(4,2)(x_2, y_2) = (4, -2).

  2. M=(12,32)M = \left(\frac{1}{2}, \frac{3}{2}\right)

    Add the coordinates: 3+4=1-3 + 4 = 1 and 5+(2)=35 + (-2) = 3; notice that adding a negative is the same as subtraction.

  3. M=(12,32)M = \left(\frac{1}{2}, \frac{3}{2}\right)

    Divide each sum by 2, even though the results are not integers: 12\frac{1}{2} and 32\frac{3}{2} are both valid coordinates.

Answer: (12,32)\left(\frac{1}{2}, \frac{3}{2}\right)

This example requires handling negative coordinates and subtraction within the sum, and it produces fractional midpoint coordinates. The negative signs are common sources of error, but careful substitution and arithmetic yield the correct result: the midpoint does not need to have integer coordinates.

3. Find the location halfway between two store sections

Problem

A coffee shop's register is located at coordinates (10,20)(10, 20) on the shop floor plan, and the supply closet is at (26,4)(26, 4). The manager wants to place a new customer pickup station exactly halfway between these two locations. What are the coordinates of the pickup station?
  1. M=(10+262,20+42)M = \left(\frac{10 + 26}{2}, \frac{20 + 4}{2}\right)

    Set up the midpoint formula by identifying the register's coordinates as (x1,y1)=(10,20)(x_1, y_1) = (10, 20) and the closet's coordinates as (x2,y2)=(26,4)(x_2, y_2) = (26, 4).

  2. M=(362,242)M = \left(\frac{36}{2}, \frac{24}{2}\right)

    Add the x-coordinates to get 10+26=3610 + 26 = 36 and the y-coordinates to get 20+4=2420 + 4 = 24.

  3. M=(18,12)M = (18, 12)

    Divide each sum by 2: 362=18\frac{36}{2} = 18 and 242=12\frac{24}{2} = 12, giving the central location.

Answer: (18,12)(18, 12)

This real-world scenario demonstrates how the midpoint formula solves a practical problem: finding a central location equidistant from two existing points. We treat the physical locations as coordinate pairs and apply the formula to determine where the pickup station should be placed so customers walking from either location travel the same distance.

Common mistakes

Where Midpoint Formula usually goes wrong
Answer came out wrong
Adding all four coordinates together and dividing by 2: M=x1+x2+y1+y22M = \frac{x_1 + x_2 + y_1 + y_2}{2}, treating the result as a single number instead of an ordered pair.
Keep the x and y sums separate: M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right) is an ordered pair with exactly two coordinates.
Subtracting the coordinates instead of adding: M=(x1x22,y1y22)M = \left(\frac{x_1 - x_2}{2}, \frac{y_1 - y_2}{2}\right).
Always add: M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right). If you need the distance or difference between points, use the Distance Formula instead.
Forgetting to divide by 2 and reporting M=(x1+x2,y1+y2)M = (x_1 + x_2, y_1 + y_2) as if it were the midpoint.
Always divide both sums by 2: the complete formula is M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right), not just the sum.
The mistakeWhy it is wrongThe fix
Adding all four coordinates together and dividing by 2: M=x1+x2+y1+y22M = \frac{x_1 + x_2 + y_1 + y_2}{2}, treating the result as a single number instead of an ordered pair.A point in the coordinate plane always has two coordinates, not one; averaging all four values into a single number destroys the geometric meaning and gives you a meaningless result.Keep the x and y sums separate: M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right) is an ordered pair with exactly two coordinates.
Subtracting the coordinates instead of adding: M=(x1x22,y1y22)M = \left(\frac{x_1 - x_2}{2}, \frac{y_1 - y_2}{2}\right).Subtraction does not give you the point halfway between two endpoints; instead it moves you away from the true center toward one side, and the result does not lie on the line segment between the original points.Always add: M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right). If you need the distance or difference between points, use the Distance Formula instead.
Forgetting to divide by 2 and reporting M=(x1+x2,y1+y2)M = (x_1 + x_2, y_1 + y_2) as if it were the midpoint.Adding the coordinates without dividing gives you the sum of the two position vectors, not the point halfway between them; this point lies far outside the segment joining the original points.Always divide both sums by 2: the complete formula is M=(x1+x22,y1+y22)M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right), not just the sum.

Tips and when to use something else

  • Think of the midpoint formula as finding the 'average point' in both the horizontal and vertical directions: the x-coordinate of the midpoint is the average of the two x-coordinates, and the y-coordinate is the average of the two y-coordinates.
  • If you need the straight-line distance between two points instead of their center, use the Distance Formula: d=(x2x1)2+(y2y1)2d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}; the Distance Formula and Midpoint Formula are often used together.
  • The order of the two points does not matter: swapping the points does not change the midpoint, since addition is commutative (a+b=b+aa + b = b + a).
  • The midpoint coordinates do not need to be integers; if the sum of the coordinates is odd, you will get a fraction or decimal, and that is the correct answer.

Frequently asked questions

Can the midpoint have coordinates that are not whole numbers?
Yes. If either sum of coordinates is odd, dividing by 2 produces a fraction or decimal, and that is the correct midpoint coordinate. For example, the midpoint of (1,2)(1, 2) and (2,3)(2, 3) is (1.5,2.5)(1.5, 2.5), which is perfectly valid even though the original points had integer coordinates.
What is the difference between the midpoint formula and the distance formula?
The midpoint formula finds the center point *between* two endpoints, whereas the distance formula measures how far *apart* those two endpoints are. Use midpoint when you need to locate a center or halfway point, and use distance when you need to measure a length.
Does it matter which point I call (x1,y1)(x_1, y_1) and which one I call (x2,y2)(x_2, y_2)?
No. Since addition is commutative, swapping the two points produces the same midpoint: x1+x22=x2+x12\frac{x_1 + x_2}{2} = \frac{x_2 + x_1}{2} and y1+y22=y2+y12\frac{y_1 + y_2}{2} = \frac{y_2 + y_1}{2}. You will always get the same answer regardless of which point is which.
How do I use the midpoint formula in a real-world situation?
Any time you need to find a location halfway between two known points—a meeting spot equidistant from two cities, the center of a line segment on an architectural blueprint, the middle value between two data points on a graph, or the center of a chord in a circle. Treat the two known locations as coordinate points and apply the formula directly.

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Reviewed 2026-09-18