The call follows the government's recent consultation on restoring ecological loss during housing construction and delivering a ten per cent boost on biodiversity post-development.
Rico Wojtulewicz, NFB head of housing and planning, said: "On small sites of up to 50 homes, we need an automated calculation process which takes into account local species and accepts onsite solutions, such as building in biodiversity to the fabric of buildings, site design and even gardens, where a management plan is attached."
The trade body has said this would reduce costs, prevent delays, and enable environmental assessments to be done coherently.
The government wants developers to use Defra's biodiversity metric to produce a plan on biodiversity net gain to submit to councils when applying for planning permission.
However, the NFB has said this could add tens of thousands of pounds to smaller development costs. It has collaborated with environmental consultants Joe's Blooms to use an automated system for small sites.
Mr Wojtulewicz said the current proposals for creating onsite habitats such as trees and ponds should also include design features that add to biodiversity.
He adds: "If you can't do the ten per cent of above onsite, you have to do it offsite, which is why we need a broader scope of what onsite means, including building fabric, site design and even garden management plans."
He quoted onsite features like bat boxes, green roofs, raised hedging and light spectrums as examples of features that should be counted as adding to biodiversity.
Joe Bloom's founder Oliver Lewis said making it easier for SMEs to comply with net gain would ensure the success of the new policy.
Brokers Hank Zarihs Associates said an automated system would help SME builders calculate more accurately how much they needed to borrow from development lenders.
The consultation closes on the 5th of April with the new regulations expected to be incorporated in the national planning policy framework before the end of 2023.
Housing minister Christopher Pincher said: "This is all part of our plan to level up the country and transform our communities into places people want to live and work. I encourage all those in the housing industry to share their views in this important consultation."
