Simple Spawn to Substrate Calculator Looking for an easy way to estimate how much grain spawn and bulk substrate to use? Our Spawn to Substrate calculator is an easy way to determine how much bulk substrate you will need based on your monotub or growing chamber. Shop our best-selling pasteurized manure substrates. Sale! Pasteurized Mushroom Substrate (5lbs)Rated 5.00 out of 5 $29.50 $24.50 Add to WishlistAlready In Wishlist Add to Wishlist Sale! Pasteurized Mushroom Substrate (10lbs) – Manure Based Bulk SubstrateRated 5.00 out of 5 $47.34 $36.50 Add to WishlistAlready In Wishlist Add to Wishlist Is this mushroom substrate calculator helpful? Have recommendations or would you like to see more detailed information? Shoot us a message on the comment box below. Submit a Comment Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website Save my name, email, and website in this browser for the next time I comment.