Since 54.4 > 10, use the Daniels formula: SRM = 0.11 + (0.69 × 54.4) SRM = 0.11 + 37.536
Notice a problem? MCU uses Lovibond (or SRM malt color) as an input. If your MCR is an MCU number, it already contains a color conversion. But to get final beer SRM, use this empirical formula derived from Dan Daniels' and Ray Daniels' work:
Now you have the knowledge to bridge the gap between historic brewing literature and modern SRM standards. Go forth and brew with color confidence.
The most widely accepted conversion is a polynomial fit, because the relationship between MCU and measured SRM is (light scattering and Maillard reactions alter final color).