How to Find Equation of Line in Excel

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. For “find equation of line in excel”, the reliable version is a short checking loop, not just the first command that appears to work. Run it on a deliberately small range first, watch how the affected cells change, and only then apply the same setup to the full sheet. 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 is what makes a data step that keeps your analysis trustworthy useful in real work: repeatable, auditable, and not dependent on memory or luck.

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. One habit worth forming early: name the cells that hold your inputs, so the formula reads in plain language instead of a string of cell addresses. A reviewer — or you in three months — can then follow the logic without decoding what B7 and D2 were supposed to mean, which is most of what makes a sheet maintainable.

In Google Sheets

If you are in Google Sheets rather than Excel, the good news is that the formula shown here is identical and the workflow barely changes — menus sit across the top instead of in a ribbon, and a few function names differ slightly, but anything you build here moves across with little or no rework. 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 “find equation of line 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