Equations in APA 7 Style: format and numbering

Equations in text and on separate lines

APA Style places a short, simple equation within the sentence. A complex equation or one that needs a number appears on a separate line so readers can see each part clearly.

Equations are not figures. They do not use the label Figure, an italic title, or a note below. Their format depends on whether they remain in the paragraph or are displayed separately.

Short equations within text

Keep an expression in the paragraph when it can be read without changing the height or spacing of the text line. Use a slash for a simple fraction and add parentheses when needed to make the order of operations clear.

When an expression needs several levels of grouping, use parentheses first, square brackets second, and braces last: {[( )]}. This sequence makes it clear which operation contains the next one.

For example: Score = {[(a + b) × c] / d}.

Example within a sentence:

The proportion was calculated with the equation p = correct responses / total responses.

The equation is part of the sentence and takes the punctuation required by that sentence. When it appears at the end, place the period after the expression.

Equations on a separate line

Display complex equations, equations with tall fractions, and equations you need to refer to later. Center the equation and place its number in parentheses near the right margin.

Displayed equation example:

Final score = (activities × 0.40) + (exam × 0.60).                  (1)

The period belongs to the sentence containing the equation. The number (1) makes later references possible and does not include the word Equation in the label.

How to number and refer to equations

Number displayed equations consecutively with Arabic numerals: (1), (2), and (3). Use the full word when referring to one in the text:

Equation 1 shows how the two parts of the grade were combined.

Do not abbreviate the reference as Eq. 1. When an equation appears in an appendix, follow the numbering for elements within an appendix and combine its letter with the number, such as Equation A1.

Spaces, signs, and symbols

Leave a space on both sides of operation and relation signs:

• correct: a + b = c
• difficult to read: a+b=c

Use a minus sign for subtraction: z − y = x. When it indicates a negative value, do not place a space between the sign and number: −8.25.

Use your word processor's subscript and superscript functions. Do not manually reduce the size of a character or move it with spaces to imitate these positions.

See also the general rules for special characters and mathematical symbols.

An equation is part of a sentence

An equation must fit the grammar of its sentence. It may be followed by a comma, period, or another mark according to its role.

Example with a continuing sentence:

Index = points earned / points possible,                            (2)

where a value near 1 indicates a greater proportion of correct responses.

The comma after the equation allows the sentence to continue in the following text.

Tools for writing equations

Use your word processor's equation editor to preserve the alignment of fractions, roots, subscripts, and superscripts. If a symbol is unavailable, it may be inserted as an image, but it must remain sharp and large enough to read.

Equation checklist

• Short expressions remain within the sentence.
• Complex equations appear on a separate line.
• Parentheses, square brackets, and braces make the order of operations unambiguous.
• Displayed equations are numbered consecutively on the right.
• The text refers to them as Equation 1, without abbreviations.
• Operators and relation signs have spaces around them.
• Every equation has the punctuation required by its sentence.
• Subscripts, superscripts, and symbols are easy to read.