Use this little Gist to calculate your contracting rate information. It's a very simple formula. Note: *YMMV* ... my formula may or may not work for you.

contracting-rate-info.js

function contractingRateInfo( options ) {
  var
    committed_days,
    committed_days_cost,
    committed_hours,
    committed_hours_cost,
    hourly,
    weekly
  ;

  committed_days = ( options.committed_days || 3 );
  committed_hours = ( options.committed_hours || 24 );
  hourly = ( options.hourly || 150 ); // Don't undervalue yourself.
  weekly = ( ( hourly * 40 ) * ( 48 / 50 ) );

  committed_hours_cost = ( hourly * committed_hours );
  committed_days_cost = ( weekly * ( committed_days / 5 ) );

  console.log( "" );
  console.log( "----- Hourly -----" );
  console.log( "Rate: $" + hourly );
  console.log( committed_hours + "-hour commitment: $" + committed_hours_cost );
  console.log( "" );
  console.log( "----- Weekly -----" );
  console.log( "Rate: $" + weekly );
  console.log( committed_days + "-day commitment: $" + committed_days_cost );
  console.log( "" );
}