# How to Use the TREND Function in Excel – MUO – MakeUseOf

With Excel’s TREND function, you can visualize your series’ performance and project the unknown values by plotting a trend line. Here’s how to use it.
Understanding what a trend is and projecting them are useful skills as trends give you an image of which direction a series is going and how hard it is going in that direction.
You can create a trend for your series in Excel using the TREND function. Furthermore, you can visualize this trend and its projected values alongside your known values to get a complete demonstration of your data.
In this article, we'll cover what a trend is, how to use the TREND function and visualize it, and how to calculate a trend's slope in Excel.
In statistics, a trend is an upwards or downwards straight line that shows where a series of data is headed to. This is mostly used in the case of time series, where a parameter's value is displayed for given times.
You can use a trend line to visualize a trend. A trend line is a straight line that best fits your series of data, and though it's likely that it won't be passing through every input, it's the closest a line can be to all the values in your series. The only way a trend line can go through every value is when your values are in a straight line already.
You can use trends to get a projected value. With the trend line, you can see where your data is headed and predict the value for a given time. The trend line shows you if your series is going upwards or downwards, and with what slope is it going in that direction.
Calculating trends is time-consuming, and prone to human error. One of the most popular methods of calculating a trend is the least square method. Luckily, Excel has incorporated this method into its TREND function.
TREND is a statistic function in Excel that takes the known Ys and the known Xs, creates a trend line, and then projects new Ys for given Xs using that trend line. The syntax is as below:

`=TREND(known_y's, [known_x's], [new_x's], [const])`

The const parameter determines how the b value in the line equation y = ax + b is calculated. If it's left blank, or TRUE, then it is calculated as it is. If it is set to FALSE, then b is set to zero, and the trends are calculated in a trend line with the y = ax equation.
TREND is mostly used to analyze past data, to see how a series has been doing in the past, whereas the FORECAST function is used to predict how a series will do in the future. However, since these two functions use the same equations, they will both return the same results when used on time series, as we will in this article.

Now that you know what the TREND function is and what it does, let's put it to use. In this sample spreadsheet, we have a time series. However, we have 10 Ys from 1 to 10, but only 8 Xs which are for the values 1 to 8. The goal is to draw a chart of the series, and its trend, using the TREND function. We will also calculate the projected value for times 9 and 10.

Now that you have your projected values from the TREND function, let's visualize it with a chart.
You now have a chart of your time series, along with their values, based on the trend line calculated by the TREND function. Notice how you can get a prediction of the Ys for times 9 and 10 with the TREND value.
Now that you know how to calculate trends and visualize them, you might wonder what exactly is the slope of this trend line. Since the trend line is a straight y = ax + b line, you can calculate the slope (a) yourself. But this is Excel and around these parts of the town, we let Excel do the calculations.
The SLOPE function in Excel is a handy function that calculates the slope for a series of data.

`=SLOPE(known_Ys, knownXs)`

Let's try and get the slope for the trend in the example from the last section. To achieve this, we're going to use the SLOPE function on the projected Ys from the TREND function.
Related: How to Add Sparklines in Excel
With Excel, you can use the TREND function to create a trend line for your series and use it to see how your series has performed, and even get a projection of the unknown values. You can also visualize this trend line by creating a line chart for it and comparing the projected Ys with the known Ys.
The TREND function is a powerful tool for managing your finance with Excel, and it's not the only one of its kind. There's an arsenal of Excel functions that you can utilize to make managing your finances easier.
Whether you are an accountant or a finance professional, you should know these Excel formulas.
Amir is a pharmacy student with a passion for tech and gaming. He likes playing music, driving cars, and writing words.