Transpose of a Matrix

The transpose of a matrix swaps its rows and columns; use it when matrices need to match dimensions for multiplication or to solve systems of equations.

(AT)ij=aji(A^{T})_{ij} = a_{ji}

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What each symbol means

What Transpose of a Matrix takes
AA
ii
jj
Transpose of a Matrix
SymbolMeaning
AAThe original matrix—a rectangular array of numbers arranged in rows and columns that we will transpose.
iiThe row index of an element in the transposed matrix ATA^T; it tells you which horizontal row from top to bottom (1st, 2nd, etc.).
jjThe column index of an element in the transposed matrix ATA^T; it tells you which vertical column from left to right (1st, 2nd, etc.).

When to use it

Transpose when you need to flip a matrix's rows and columns, often to align dimensions for multiplication or to reorganize data.

Level

Usually taught in: Pre-Calculus

Worked examples

1. Transpose a rectangular 2×3 matrix

Problem

Find the transpose of A=(123456)A = \begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \end{pmatrix}.
  1. A=(123456)A = \begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \end{pmatrix}

    The matrix AA has 2 rows and 3 columns.

  2. Columns of A:(14),(25),(36)\text{Columns of } A: \begin{pmatrix} 1 \\ 4 \end{pmatrix}, \begin{pmatrix} 2 \\ 5 \end{pmatrix}, \begin{pmatrix} 3 \\ 6 \end{pmatrix}

    Identify the three columns of AA: [1, 4], [2, 5], and [3, 6].

  3. These columns become rows in AT\text{These columns become rows in } A^{T}

    In the transpose, each column of AA becomes a row of ATA^T.

  4. AT=(142536)A^{T} = \begin{pmatrix} 1 & 4 \\ 2 & 5 \\ 3 & 6 \end{pmatrix}

    Assemble the columns-as-rows into the final transposed matrix with 3 rows and 2 columns.

Answer: AT=(142536)A^{T} = \begin{pmatrix} 1 & 4 \\ 2 & 5 \\ 3 & 6 \end{pmatrix}

Transpose swaps rows and columns: each row becomes a column, and each column becomes a row. The dimensions also flip from 2×32 \times 3 to 3×23 \times 2.

2. Transpose a 3×3 matrix with negatives and fractions

Problem

Find the transpose of B=(2112304521)B = \begin{pmatrix} 2 & -1 & \frac{1}{2} \\ 3 & 0 & -4 \\ 5 & 2 & 1 \end{pmatrix}.
  1. B=(2112304521)B = \begin{pmatrix} 2 & -1 & \frac{1}{2} \\ 3 & 0 & -4 \\ 5 & 2 & 1 \end{pmatrix}

    Write the matrix clearly, noting which elements are negative and which are fractions.

  2. (BT)row 1=(B)col 1=(235)(B^{T})_{\text{row }1} = (B)_{\text{col }1} = \begin{pmatrix} 2 \\ 3 \\ 5 \end{pmatrix}

    The first row of BTB^T comes from the first column of BB: we take b11=2b_{11} = 2, b21=3b_{21} = 3, b31=5b_{31} = 5.

  3. (BT)row 2=(B)col 2=(102)(B^{T})_{\text{row }2} = (B)_{\text{col }2} = \begin{pmatrix} -1 \\ 0 \\ 2 \end{pmatrix}

    The second row of BTB^T comes from the second column of BB: we take b12=1b_{12} = -1, b22=0b_{22} = 0, b32=2b_{32} = 2.

  4. (BT)row 3=(B)col 3=(1241)(B^{T})_{\text{row }3} = (B)_{\text{col }3} = \begin{pmatrix} \frac{1}{2} \\ -4 \\ 1 \end{pmatrix}

    The third row of BTB^T comes from the third column of BB: we take b13=12b_{13} = \frac{1}{2}, b23=4b_{23} = -4, b33=1b_{33} = 1.

  5. BT=(2351021241)B^{T} = \begin{pmatrix} 2 & 3 & 5 \\ -1 & 0 & 2 \\ \frac{1}{2} & -4 & 1 \end{pmatrix}

    Assemble all rows to construct the final transposed matrix.

Answer: BT=(2351021241)B^{T} = \begin{pmatrix} 2 & 3 & 5 \\ -1 & 0 & 2 \\ \frac{1}{2} & -4 & 1 \end{pmatrix}

Transpose means (BT)ij=bji(B^T)_{ij} = b_{ji}. Notice that negative numbers and fractions stay exactly the same; only their positions change. For instance, 4-4 was at position (2, 3) in BB and moves to position (3, 2) in BTB^T.

3. Use transpose to rearrange video game score data

Problem

A video game records scores by difficulty level (rows: Easy, Normal, Hard) and stage (columns: 1, 2, 3) in matrix SS. You need stages as rows to analyze them separately. Find STS^{T} where S=(5075906085957088100)S = \begin{pmatrix} 50 & 75 & 90 \\ 60 & 85 & 95 \\ 70 & 88 & 100 \end{pmatrix}.
  1. S=(5075906085957088100) (rows = difficulties, columns = stages)S = \begin{pmatrix} 50 & 75 & 90 \\ 60 & 85 & 95 \\ 70 & 88 & 100 \end{pmatrix} \text{ (rows = difficulties, columns = stages)}

    The original matrix has difficulties as rows and stages as columns.

  2. Column 1 of S=(506070) (Stage 1 scores across difficulties)\text{Column 1 of } S = \begin{pmatrix} 50 \\ 60 \\ 70 \end{pmatrix} \text{ (Stage 1 scores across difficulties)}

    Identify that column 1 contains all Stage 1 scores for each difficulty.

  3. Columns 2 and 3: (758588),(9095100)\text{Columns 2 and 3: } \begin{pmatrix} 75 \\ 85 \\ 88 \end{pmatrix}, \begin{pmatrix} 90 \\ 95 \\ 100 \end{pmatrix}

    Columns 2 and 3 contain Stage 2 and Stage 3 scores for all difficulties.

  4. ST=(5060707585889095100) (rows = stages, columns = difficulties)S^{T} = \begin{pmatrix} 50 & 60 & 70 \\ 75 & 85 & 88 \\ 90 & 95 & 100 \end{pmatrix} \text{ (rows = stages, columns = difficulties)}

    After transposing, stages become rows and difficulties become columns, making it easy to compute average score per stage.

Answer: ST=(5060707585889095100)S^{T} = \begin{pmatrix} 50 & 60 & 70 \\ 75 & 85 & 88 \\ 90 & 95 & 100 \end{pmatrix}

The transpose flips the meaning of rows and columns: data organized by difficulty is now organized by stage. This rearrangement helps answer questions like 'which stage has the highest average score?' by letting you compute averages across each row.

Common mistakes

Where Transpose of a Matrix usually goes wrong
Answer came out wrong
When transposing A=(1234)A = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}, students sometimes write (3142)\begin{pmatrix} 3 & 1 \\ 4 & 2 \end{pmatrix} (90-degree rotation) instead of (1324)\begin{pmatrix} 1 & 3 \\ 2 & 4 \end{pmatrix} (transpose).
Use the definition to verify: position (1, 2) in ATA^T should equal position (2, 1) in AA, which is 3, not 1. If your answer doesn't match this rule, rotate back and transpose instead.
A student transposes a 2×32 \times 3 matrix but writes the result as still 2×32 \times 3, trying to fill nine positions instead of six.
Always check: if AA has 2 rows and 3 columns, then ATA^T has 3 rows and 2 columns. Count the dimensions first, and reshape your result accordingly.
When transposing (2345)\begin{pmatrix} 2 & -3 \\ 4 & 5 \end{pmatrix}, a student writes (2435)\begin{pmatrix} 2 & 4 \\ 3 & 5 \end{pmatrix}, accidentally dropping the negative sign on 3-3.
Remember that (AT)ij=aji(A^T)_{ij} = a_{ji} only swaps indices—the value stays the same. The element 3-3 at position (1, 2) becomes the element 3-3 at position (2, 1).
The mistakeWhy it is wrongThe fix
When transposing A=(1234)A = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}, students sometimes write (3142)\begin{pmatrix} 3 & 1 \\ 4 & 2 \end{pmatrix} (90-degree rotation) instead of (1324)\begin{pmatrix} 1 & 3 \\ 2 & 4 \end{pmatrix} (transpose).Rotation and transpose look similar visually, but rotation is a different transformation; transpose specifically swaps rows and columns according to (AT)ij=aji(A^T)_{ij} = a_{ji}.Use the definition to verify: position (1, 2) in ATA^T should equal position (2, 1) in AA, which is 3, not 1. If your answer doesn't match this rule, rotate back and transpose instead.
A student transposes a 2×32 \times 3 matrix but writes the result as still 2×32 \times 3, trying to fill nine positions instead of six.If AA is m×nm \times n, then ATA^T must be n×mn \times m; ignoring this dimension flip creates an impossible or incorrect matrix.Always check: if AA has 2 rows and 3 columns, then ATA^T has 3 rows and 2 columns. Count the dimensions first, and reshape your result accordingly.
When transposing (2345)\begin{pmatrix} 2 & -3 \\ 4 & 5 \end{pmatrix}, a student writes (2435)\begin{pmatrix} 2 & 4 \\ 3 & 5 \end{pmatrix}, accidentally dropping the negative sign on 3-3.Transpose only rearranges positions; it does not modify element values, signs, or any other property of the numbers themselves.Remember that (AT)ij=aji(A^T)_{ij} = a_{ji} only swaps indices—the value stays the same. The element 3-3 at position (1, 2) becomes the element 3-3 at position (2, 1).

Tips and when to use something else

  • The notation ATA^T (sometimes AA' in older textbooks) means transpose; both refer to the same operation.
  • Transpose is useful for matrix multiplication: if matrices don't align for multiplication, check whether transposing one will fix the dimension compatibility.
  • Do not confuse transpose with the inverse: ATA^T and A1A^{-1} are different operations (use Inverse of a 2x2 Matrix to find which matrix 'undoes' multiplication by AA).
  • A square matrix where A=ATA = A^T is called symmetric; these matrices have special properties and appear frequently in applications like statistics and physics.

Frequently asked questions

Do I have to transpose square matrices differently than rectangular ones?
No, the rule (AT)ij=aji(A^T)_{ij} = a_{ji} applies to any matrix shape. For a 3×33 \times 3 square matrix, you flip rows and columns just as you would for a 2×32 \times 3 rectangular matrix. The only difference is that a square matrix's shape stays square, while a rectangular matrix's dimensions swap.
What happens if I transpose a transpose?
(AT)T=A(A^T)^T = A—you get back the original matrix. This makes intuitive sense: flipping rows and columns twice returns everything to its starting position.
Can I transpose a row vector or column vector?
Yes. A row vector (1 row, many columns) transposes to a column vector (many rows, 1 column). For example, [1,2,3]T=(123)[1, 2, 3]^T = \begin{pmatrix} 1 \\ 2 \\ 3 \end{pmatrix}. This is especially useful in matrix multiplication.
Why is transpose useful in practice?
Transpose rearranges data for different analyses (like reorganizing customer records to analyze trends by column instead of row), enables matrix multiplication when dimensions initially don't match, and defines important concepts like symmetric matrices. It's fundamental in statistics, engineering, and computer science.

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Reviewed 2026-09-18