Roasting times will vary depending on the thickness of your fillet. Using a meat thermometer (out of the oven - resting will increase the temperature) is the best way to check the level of doneness. The following guide should help:
45-50°C = Rare (cool red centre)
50-55°C = Medium Rare (warm red centre)
55-60°C = Medium (warm pink centre)
60-65°C = Medium Well Done (slightly pink centre)
65-70°C = Well Done (little or no pink centre)
70°C + = Very Well done (no pink centre)
Always carve meat at the last minute, otherwise the flesh will turn grey.
The best way to ensure accurate measurement of ingredients is with Metric Kitchen Scales. They are inexpensive and take up very little space. Click
HERE for the ones I use. For U.S. option click
HERE.