**Method 1 – Using an Exponential Formula to Calculate Bacterial Growth Rate in Excel**

Bacteria in cultures follow exponential growth. From experiments, we get the formula to calculate the growth rate. The **Growth Rate (Âµ)** formula is

`Â Âµ = ((log10 N - log10 N0) 2.303) / (t - t0)`

Here,

**N **= Number of Bacteria at **t** second

**N _{o }**= Number of Bacteria at

**t**second

_{o}**t **= a particular time in the growth period

**t _{o }**= starting time of bacteria culture

**Step 1:** Write the formula in any blank cell (i.e., **E6**).

`= ((log10 N - log10 N0) 2.303) / (t - t0)`

**Step 2: **Press** ENTER,**Â Drag the **Fill Handle** to display the **Growth Rate** for **Bacteria Culture 1** as depicted in the image below.

**âž¤ **Repeat **Steps 1** and **2** in order to bring out the **Growth Rate** for **Bacteria Culture 2 **similar to the picture below.

**Step 3: **After getting the **Growth Rate** percentages for **Bacteria Culture 1**, apply the **AVERAGE** function. The **AVERAGE** function calculates the average **Growth Rate** percentages out of those resultant percentages.

Type the below formula

`=AVERAGE(E5:E14)`

**âž¤ **Following **Step 3**, apply the **AVERAGE** formula to calculate the average **Growth Rate** of bacteria in **Culture 2**.

**Step 4: **Combine the two average **Growth Rate**s into an **Accumulated Average Growth Rate** using an **AVERAGE** formula. Use the formula written below

`Â =AVERAGE(E15:F15)`

**Step 5: **Hit the **ENTER** key, and you get the **Accumulated Average Growth Rate** for the two **Bacteria Culture**s.

Calculating a bacterial culture’s Growth Rate requires experimental data, and the formula must be compatible with the bacteria’s characteristics. We calculate the Bacterial Growth Rate using a typical empirical formula. Use yours that is compatible with the bacteria’sÂ characteristics.

To display the **Growth Rate** in percentages, you have to pre-formatted the cell in percentage **Category** from the **Format Cells** window.

**âž¤ **Select a range of cells then Press Keyboard shortcuts **CTRL+1** altogether to bring out the **Format Cells** window. Select the **Number **section > Choose **Percentage **as **Category** > Assign the number of **Decimal Places** you want your data in.

Click **OK**.

**Method 2 – Using Chart Method to Display the Growth Rate**

We used an **Exponential Formula** to calculate the **Growth Rate** of a Bacteria Culture. Use the dataset to display a **Curve Chart** from where we extract the **Exponential Formula**. By looking at the formula, find out the **Growth Rate** for each Bacteria Culture. The typical **Exponential Formula** of Bacteria Culture is

`y=b*emx`

In the formula,

**y **= yielding number of bacteria after **x** time.

**b **= Constant.

**m **= Bacteria Growth Rate

**Step 1:** Select the two columns (i.e., **Time** vs **Number for Bacteria Culture 1**). Then Go to the **Insert** tab > Select a **Chart Type** (shown in the screenshot) from **Scatter **options (from the **Charts** section).

**Step 2:** The **Chart** appears **Right Click** on the **Chart**. The **Context Menu** pops up. From the **Context Menu**, Select **Select Data** from the options.

**Step 3:** The **Select Data** **Source** window appears. There is an added data source already. Add the **bacteria culture 2** entries as another data source. Click on **Add** in the **Select Data Source** window.

**Step 4:** The **Edit Series** window opens up. Insert the respected data in **Series X** and** Y** values. Give the **Series** a Name (i.e., **Number of Bacteria (Culture 2)**).

Click **OK**.

**Step 5:** Clicking **OK** on the **Edit Series** dialog box takes you to the **Select Data Source** window again. The two data sources mean you’ll have two **Curves** on the **Chart** of the two equations.

Click on **OK**.

**âž¤ **Your expectations, you have two **Curves** on the **Chart**. One is there for **Culture 1** and the other for **Culture 2** as depicted in the following image.

**Step 6:** As we want to insert the formulas for each **Curve**. Click on any curve (i.e., **Orange Colored**) then **Right Click** on it.

The **Context Menu** appears. From the **Context Menu**, Select **Add Trendline**.

**Step 7:** The** Format Trendline** side common box appears. From the **Format Trendline **command box, Choose **Exponential **as **Trendline** **Options**. **Scroll Down**.

**Step 8:** See an option saying **Display Formula on Chart**. Check the option as shown in the picture below.

**Step 9:** Repeat **Step 6**, **7,** and** 8** for the** Blue Colored** curve and you get the exponential equations in the same colors for both **Curves**.

**âž¤ **Add the **Chart** and **Axis** title, click on the big **PLUS Icon **button. A couple of options appear, Tick the **Axis** and **Chart Title** to display them on the chart.

**âž¤ **Assign suitable titles for the **Chart **and **Axis Title**. The entire chart looks similar to the image below.

You see the equations (i.e., **y=7566.7e ^{0.0605x} and y=7525.3e^{0.0594x}**) for both data sources. By comparing the equations to the typical

**Exponential Equation**(i.e.,

**Y=b*e**), you can say that the

^{mx}**Growth Rate**of the

**Bacteria Culture 1**and

**2**are

**0.605**or

**6.05%**and

**0.0594**or

**5.94%**respectively.

Find the **Growth Rate** just by acquiring the equations.

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