Occasionally, there will be a home so leaky the blower door cannot achieve 50 Pascals steady state for entry into Snugg.

The Energy Conservatory has a tool to estimate 50Pa with a lower steady state reading.

Choose "TEC Calculators":

Then "B.P. Calculators":

Then "Can't Reach 50Pa":

Enter the building pressure you can reach in the "Building Pressure (Pa)" and the CFM reading at the pressure you can reach in "Airflow (CFM)". The estimated CFM50 are displayed in the "Airflow (CFM50)" field.