How you share the cost of raising your child is for you and your ex-partner to decide. For example, you might agree to 'split the difference', or vary it according to how much money you each earn.
The contribution made by the paying parent is what's usually called "child maintenance".
For more ideas about how to share the costs of raising your child, read what to include in your family-based arrangement.
If you're worried about talking to your child's other parent about child maintenance, get further help with talking about child maintenance.