Oh, ok.. I think I know what your asking about.. I always watch time and sales to see if the order Im placing might seem too big and stick out.. You always want to blend.. but another way to decide would be to visit Cryptocurency Market Capitalizations: https://coinmarketcap.com/assets/singulardtv/#markets

Here you can see the 24hour volume and then you will know how much buying and selling there is in compairison to what your planning to spend.