# Writing formulas

Formulas are human-readable, only need to be entered once, and don’t have to be remembered—so everyone in your organization can easily work with them.

## Understanding formulas

**Formulas that anyone can understand**

With Runway, you can write formulas that anyone can understand.

Human-readable formulas use natural language labels for drivers, instead of cell references, so ‘Runway 🛫’ becomes ‘Cash 💵’ divided by ‘Burn 🔥’:

### Formulas you don’t have to remember

In Runway, formulas are unique and only have to be entered once to be used anywhere across the platform.

Once you’ve entered the formula for ‘Burn 🔥’, you can easily reference that driver in any model, on any page, or in charts to calculate or visualize. No need to remember or re-enter the same formula each time.

### Formulas that show values as time series

Unlike spreadsheet formulas that are cell-based, Runway formulas are row-based.

Each driver has a unique formula that shows its values as a time series, and uses different data sources to calculate past and future values.

- Actuals are calculated using data pulled from integrations or other drivers, or data that’s been manually added.

- Forecasts are calculated based on data from driver formulas and plans.

While building a model, you can use either a forecast and or an actual formula for a given time period. Each formula affects different parts of the time series.

## Working with formulas

### Creating a forecast formula

Forecast formulas calculate future values. For example, say you want to create a formula to calculate the ‘Months of Runway 🛫’:

- Go to the cell in your model that contains the ‘Months of Runway 🛫’ driver. If you don’t have the correct driver in your model, follow these steps to create one.

- Double-click on the
*Forecast Formula*column to the right, and enter your formula.

### Creating an actual formula

Let’s say you want to use your QuickBooks integration to create an actuals formula for ‘Months of Runway 🛫’. This is how it would look:

- To add an actuals formula, double-click on the
*Actuals Formula*column to the right of the driver.

- Next, link the actuals or historical data from your integrations or databases. They’ll appear in the
*External Drivers*section of the autofill as you type, and can be identified by the icon or logo for your tool.

- Once your actuals are populated, you can also override them by manually entering values into cells.

### Using operators in formulas

You can use these typical operators in your formulas:

`+`

for addition

`-`

for subtraction

`*`

for multiplication

`/`

for division

Runway also supports a variety of mathematical functions to perform complex calculations without extensive manual work. You can access these frequently-used options in the *Functions* section of the autofill as you type:

Function name | Syntax | Usage |

`sum()` | sum(reference) | Returns the sum of a database field or dimensional driver reference. |

`count()` | count(reference) | Returns the number of values in a database field or dimensional driver reference. |

`if()` | if(logical_expression, value_if_true, value_if_false) | Returns one value if a logical expression is true and another if it is false. |

`round()` | round(value, [places]) | Rounds a number to a certain number of decimal places according to standard rules. |

`min()` | min(reference…) | Returns the numerical minimum value in a database field, dimensional driver reference, or set of numeric evaluations. |

`max()` | max(reference…) | Returns the numerical maximum value in a database field, dimensional driver reference, or set of numeric evaluations. |

You can apply the operators and functions to:

- Individual drivers (e.g.
`cash`

/`burn`

).

- Driver groups (e.g. summing all the values of a driver group with sales expanded by a specific dimension).

- Databases (e.g. counting the number of employees in one department).

### Editing a formula

To edit an existing formula, you have 3 options:

- Double-click on the formula cell.

- Click the
**𝑓 symbol**that appears next to the driver's name when hovering over the corresponding cell.

- From the detail view of a driver, click on the formula.

### Fixing formula-related errors

If you see a warning next to a formula, it means the formula contains an error. Here are the most common errors and how to fix them:

Missing operator | Locate the red underline and add the missing operator. |

Missing expression at the end of formula | Add the missing expression, typically a closing parenthesis. |

Formula contains deleted dependency | Replace the deleted driver with a valid one. It will be highlighted with a red outline in the formula so you can quickly identify it. |

Dependency loop with driver | Rewrite the formula for the driver that’s generating the dependency loop. |

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Last updated on July 14, 2023