For example on a recipe node, exposing a "yield" field on a rendered node to recalculate ingredient quantity values
I dont think there is any module that you can use, you can try hook_node_view_alter hook to change the rendered.
If the module wishes to act on the rendered HTML of the node rather than the structured content array, it may use this hook to add a post_render callback. Alternatively, it could also implement hook_preprocess_node(). See drupal_render() and theme() documentation respectively for details.
Check hook_entity_view_alter too
If you want to change in the node create form, there is Conditional Fields Module.
Define dependencies between fields based on their states and values. Conditional Fields for Drupal 7 is an user interface to the new States API, plus the ability to modify fields appearance and behavior on certain conditions when viewing content.
Computed Field module can be configured to work just the way you need:
You can also choose whether to store your computed field values in the database with other content fields, or have them "calculated" on the fly during node views.