In Excel: use =SLOPE(known_ys, known_xs) and =INTERCEPT(known_ys, known_xs) — together they give the two coefficients of the best-fit straight line, y = slope × x + intercept.
Syntax
Arguments
| Argument | Description | |
|---|---|---|
known_ys | required | The dependent values — the thing being predicted. |
known_xs | required | The independent values, the same size as known_ys. |
Related functions
Select a cell for the slope and type =SLOPE(.
Select the y values (the outcome) FIRST, then a comma, then the x values.
Repeat in a second cell with =INTERCEPT and the same argument order.
Combine them as intercept + slope × x to predict any new value.
What this does
SLOPE and INTERCEPT return the two numbers that define the least-squares regression line through a set of points. SLOPE is the rate of change — how much y moves per unit of x — and INTERCEPT is where the line crosses at x = 0. Written out they reproduce exactly the trendline equation a chart displays, which makes them the way to use a fitted line in calculations rather than merely look at one. Watch the argument order: the y values come first, which is the reverse of how most people say "x against y". 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 “get the slope of a line 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 visual that makes the number obvious at a glance into a method you can reuse, explain, and defend when the workbook leaves your screen.
A worked example
Units produced in B2:B40 and total cost in C2:C40: =SLOPE(C2:C40, B2:B40) returns the variable cost per unit and =INTERCEPT(C2:C40, B2:B40) the fixed cost. Predicting the cost of 250 units is then =INTERCEPT(...) + SLOPE(...)*250, which is what FORECAST.LINEAR does in a single call. SLOPE and INTERCEPT take a chart trendline out of the picture and put it into the model, where it can drive actual calculations. If there is any chance you will reuse this, drop it into a small template tab right now: a labelled input area on the left and the formula beside it, checked once against the tool above. Next time the same question comes up, the answer is a single paste away instead of a rebuild from memory.
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. Nothing on this page is behind a login: the tool runs entirely in your browser, the formula is shown in full with one-click copy, and the steps work the same on Windows and Mac. That is the whole promise here — the exact answer, a way to prove it on your own numbers, and just enough context to make it stick. Here is the takeaway for “get the slope of a 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
- Reversing the arguments — y comes first in both functions, and swapping them silently returns a different line.
- Extrapolating far beyond the observed x range, where a straight line has no support from the data.
- Fitting a line to plainly curved data; check the scatter plot before trusting either coefficient.
Frequently asked questions
Which argument comes first?
The y values — the thing being predicted. =SLOPE(known_ys, known_xs).
How do I get the trendline equation from a chart into cells?
SLOPE and INTERCEPT return exactly those two coefficients, so you can use the fitted line in formulas instead of reading it off the chart.
How do I predict a value?
=INTERCEPT(ys,xs) + SLOPE(ys,xs)*newX, or the shorter =FORECAST.LINEAR(newX, ys, xs).