# How to reference a pervious row in a Math calculation

**URL:** <https://community.glideapps.com/t/how-to-reference-a-pervious-row-in-a-math-calculation/70212>\
**Category:** Ask for Help\
**Created:** [January 29, 2024, 5:37pm UTC](https://community.glideapps.com/t/how-to-reference-a-pervious-row-in-a-math-calculation/70212 "2024-01-29T17:37:17Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![Darren\_Murphy](https://sea2.discourse-cdn.com/flex002/user_avatar/community.glideapps.com/darren_murphy/32/47326_2.png) [@Darren\_Murphy](https://community.glideapps.com/u/Darren_Murphy)\
**Post date:** [January 29, 2024, 6:00pm UTC](https://community.glideapps.com/t/how-to-reference-a-pervious-row-in-a-math-calculation/70212/2 "2024-01-29T18:00:42Z")

</div>

- Start by adding a RowIndex to your table by following the second method described [here](https://community.glideapps.com/t/how-do-i-create-an-auto-incrementing-row-number-with-glide-tables/39572).
- Add a Math column that subtracts 1 from the RowIndex
- Add a Single Value column. It should target your table and take the N from start Meter Reading value, where N is the Math column.

Here is how that would look:

 ![CleanShot 2024-01-30 at 01.59.54@2x](https://us1.discourse-cdn.com/flex002/uploads/glideapps/original/3X/8/7/879593a85e566e0fde44c4c78adbc3c7c3bc7ba5.jpeg)

---

_[View the full topic](https://community.glideapps.com/t/how-to-reference-a-pervious-row-in-a-math-calculation/70212)._