Even in Photoshop, you can't convert an image from RGB to CMYK and then back again without losing or altering some of the color information. EDIT: You mention a couple of times in your comments that you just want "RGB values in percentage."
To take color matching in your hands, design within the CMYK color space and then convert to RGB yourself, without losing any colors. Or, if your software doesnβt support the CMYK color space, use an online RGB to CMYK converter to check which colors of your design are out of CMYK color space and adjust those. No, none of this makes any sense. CMYK is a device-dependent color space and arbitrarily converting CMYK colors to RGB serves no purpose, as even if they were created with a specific color profile/ output device in mind, a different device (printer or whatever) would still interpret it differently and mix up the inks. that is the whole point. uRCF8x.