WooCommerce by default only accepts whole numbers as a product quantity.
If you are looking to sell products by a weight measurement you have two options:
Make your product price for the smallest measurement you sell. For example, lets say that the smallest amount of Tomatoes that someone can buy is 100g and then increments of that. Create your product and set the value to however much 100g costs. Customers can then order 100g x quantity. In the case of a kilogram, they would order 10 of the product. Use either the product title or description to clarify to customers that this is 100g.
The other option would be use a product like Measurement Price Calculator. It’s function would be similar, however it would give you the option to charge based on the product weight that you’ve entered, instead of a fix product price. This would allow customer to input the weight that they want, then calculate the price based on that.
