> ## Documentation Index > Fetch the complete documentation index at: https://calcs.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Typical Formula References > A quick guide showing how to use formulas and references in Calcs.com and typical ones you may encounter in our calculators. Using Reference IDs helps reduce duplicate inputs, keeps values consistent, and allows your calculations to automatically update when inputs change. This is especially important in engineering calculations, where the same value is often used in multiple places. By referencing a single value, you minimize the risk of input errors, avoid mismatched assumptions, and ensure that updates automatically track throughout the calculator. This not only saves time, but also improves accuracy, transparency, and confidence in the results. Anywhere you can type a value, you can use "Reference IDs", also known as "Formula References" to use already inputted or calculated values. For any of the existing variables within a calculator, you can find the corresponding formula reference by opening the dropdown tab, which is located next to any calculated or inputted value- simply by clicking on the text. Image (2) All of these values are unit-aware, meaning they’ll automatically handle unit conversions (we’ll also check that units are convertible). These often differ per calculator, but some common ones are outlined below: ## Common Beam Reference IDs | Property | Description | Reference ID | Units | | -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ | ------------- | ----- | | Total Material Length | Typically in our beam calculators, this is the plan length from start to end including any intermediate supports | L | ft | | Maximum Position From Left | Maximum position from the left, adjusted for support location based on the user’s selection of Plan or Inclined view. | x\_max | ft | | Total Start Trib. Width | Tributary width at the start of the beam (at indicated start location) | TW\_s | ft | | Typical Yield Strength | Relevant for our steel beam calculators, this value is either a user input or a typical value from the preferred specifications outlined in AISC | Fy, F\_y\_typ | psi | | Number of Plies | Relevant for our wood beam calculators, used to indicate how many plies are fastened together along the flat side | n\_com | - | In these calculators, values from Project Defaults can also be used. For example, typical bearing length is entered as `projectDefault("l_b", 3.5)`. Check out our [Project Defaults Cheat Sheet ](/docs/projects/project-defaults/project-defaults-cheat-sheet)for a more comprehensive list of what can be referenced in your calculators! ## Common Column Reference IDs | Property | Description | Reference ID | Units | | :------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------- | :------------ | :---- | | Column Height | Typically in our column calculators, this is the total height of the column from start to end including any intermediate supports | L | ft | | Default Load Eccentricity for Bending about X-axis | Default value set for the axial eccentricity in bending about the strong axis. | e\_x | in | | Default Load Eccentricity for Bending about Y-axis | Default value set for the axial eccentricity in bending about the weak axis. | e\_y | in | | Total Start Trib. Width | Tributary width at the start of the column for lateral distributed loads (at indicated start location) | TW\_s | ft | | Typical Yield Strength | Relevant for our steel column calculators, this value is either a user input or a typical value from the preferred specifications outlined in AISC | Fy, F\_y\_typ | psi | | Number of Plies | Relevant for our wood column calculators, used to indicate how many plies are fastened together along the flat side | n\_com | - | | Largest Hole Size | Relevant for our wood column calculators, used in consideration for drilled holes for holdown fasteners | d\_hole | in | You can use any of these values in a formula as well. For example, to place a support in the center of your column you can simply type in "L/2" for simplicity. ## How beam span length (L) is measured For Calcs.com beam calculators, **L** refers to the full plan length of the member, measured from the start of the beam to its end, including any intermediate supports. It is *not* just the clear span between two adjacent supports. This matters most on multi-span beams. If you have a 3-support beam with a 10 ft back span and a 10 ft front span, **L** is the total 20 ft, not either 10 ft segment on its own. Intermediate supports are then defined by their position along that total length, not by breaking the member into separate spans. Wood beam sheet showing Beam Plan Length set to 20 ft with pinned supports at 0, 10, and 20 ft If you set **L** to a single clear-span value on a multi-support beam, you'll under-report the true length of the member and the calculator will use the wrong geometry for shear, moment, and deflection. Always enter the plan length end to end. The same convention applies to **Column Height (L)** in column calculators. It is the total height of the column from start to end, including any intermediate lateral supports (see the Common Column Reference IDs table above). ## Related * [How to enter beam supports (imperial units)](/docs/running-calculations/setting-up-a-calculation/geometry-and-supports/how-to-enter-beam-supports-imperial-units) * [How to enter beam supports (metric units)](/docs/running-calculations/setting-up-a-calculation/geometry-and-supports/how-to-enter-beam-supports-metric-units) * [How to cantilever or overhang a beam (fixed or propped)](/docs/running-calculations/setting-up-a-calculation/geometry-and-supports/how-to-cantilever-or-overhang-beam-fixed-or-propped)