In Excel: click the chart, open the ➕ Chart Elements button and tick Trendline — then right-click the line ▸ Format Trendline to pick the type and show the equation and R².
On this page7
6 pairs
R² = 0.9962
Intercept = 0.1667
What this does
A trendline is a fitted line drawn through a data series: linear by default, with exponential, logarithmic, polynomial, power and moving-average alternatives in the Format Trendline pane. Two checkboxes at the bottom of that pane matter more than the line itself — "Display Equation on chart" and "Display R-squared value on chart". The equation lets you reproduce the fit in a formula, and R² tells you how much of the variation the line actually explains, which is the difference between a trend and a decoration. Excel also exposes the same maths as worksheet functions: SLOPE, INTERCEPT, RSQ, LINEST and TREND. Keep the inputs visible and clearly labelled and the whole thing stays auditable — anyone who opens the file later, including you, can see at a glance exactly what feeds the result and change one assumption without hunting through the formula. Treat “add line equation in excel” as a small repeatable workflow rather than a one-off click you hope to remember next time. Use a small test block before the live file, so any surprise in the affected cells shows up while it is still harmless. When a formula is involved, keep the inputs labelled beside it, reference cells instead of typing values, and apply number formatting only after the result checks out. That turns a layout choice that keeps the sheet readable and sortable into a method you can reuse, explain, and defend when the workbook leaves your screen.
A worked example
Twelve months of revenue in B2:B13 against month numbers in A2:A13. Click the chart ▸ ➕ ▸ Trendline ▸ Linear. Right-click the line ▸ Format Trendline ▸ tick Display Equation and Display R-squared. If the chart shows y = 3,120x + 41,500 and R² = 0.87, revenue is rising about €3,120 a month and the straight line explains 87% of the variation. The same numbers without a chart: =SLOPE(B2:B13,A2:A13) returns 3120, =RSQ(B2:B13,A2:A13) returns 0.87. A trendline turns a scatter of points into a stated rate of change, and the equation plus R² is what makes that statement defensible instead of a line someone drew through the noise. A practical tip before you scale it up: build it once on a small block of test data, confirm the number against the tool on this page, and only then point it at your real sheet. That one habit catches almost every mistake while it is still cheap to fix, long before a wrong figure reaches a report or a colleague.
In Google Sheets
Everything above works in Google Sheets too. Excel and Sheets share the formula syntax used here; only the surrounding menus are arranged differently. That portability is deliberate — learn it once and it follows you between the two tools and across Windows and Mac. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top, the tool proves it, and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. Here is the takeaway for “add line equation in excel”: copy the answer if you are busy, but if you have a spare few minutes, rebuild the example in Excel yourself with the tool above open beside it. That single pass — type it, run it, watch the result move when you change an input — is what turns a formula you found into a technique you trust. Keep your inputs labelled and referenced, never hard-coded, and the same sheet stays correct and auditable as it grows. Done that way, you will not need to look this up again, and you will be the person others ask.
Common mistakes
- Fitting a high-order polynomial because it hugs the points — an order-6 fit through 12 points has almost no predictive value and a flattering R².
- Adding a trendline to a bar chart of categories, where the x-axis has no numeric meaning.
- Quoting the slope without R², which hides how well the line actually fits.
- Forecasting far beyond the data and presenting the extension as a measurement rather than an assumption.
- Leaving unequal time gaps in the x values while treating them as evenly spaced — use a scatter chart with real x values.
Frequently asked questions
How do I add a trendline in Excel?
Click the chart, press the ➕ Chart Elements button and tick Trendline. On Mac use Chart Design ▸ Add Chart Element ▸ Trendline.
How do I show the trendline equation?
Right-click the trendline, choose Format Trendline, and tick "Display Equation on chart" and "Display R-squared value on chart" at the bottom of the pane.
What does R-squared mean?
The share of the variation in your data that the fitted line explains, from 0 to 1. R² = 0.87 means 87%. A low R² means the line is drawn but the relationship is weak.
Can I get the trend without a chart?
Yes — =SLOPE(known_ys, known_xs) and =INTERCEPT(known_ys, known_xs) give the same line, =RSQ() gives R², and =TREND() returns fitted values for new x inputs.