Minimum viable traffic is the volume of traffic you need on your website to sustain your business and marketing operations. It allows you to calculate the volume of traffic you need to remain profitable and in business.

So how do you calculate this? First, you need:

Minimum viable sales = 20k per month
E-commerce conversion rate of website = 1%
This means that every 1 in 100 visitors make a purchase when they land on your website

Average website order value = \$70

The first step is to calculate the additional orders you need to hit your minimum viable sales number.
Additional orders to get revenue of 20k = proposed salve/average order value
= 20,000 / 70 = 286 orders

Next, you need to calculate the volume of traffic you need to generate these orders.
Volume of traffic to generate 286 orders = additional orders / e-commerce conversion rate
= 286/1% = 28600 visits/clicks

Average CPC = \$0.10

With this data, you can calculate how much you need to spend to generate that traffic.
You need \$2860 to generate \$20K per month