Speed: There is a weak correlation between both Speed and Turns in BFG and Speed and
Manoeuvrability in RT. In BFG, ships up to (and including) Light Cruisers are generally fast and have a Turn rate of 90°. In RT, the same ships have a higher Manoeuvrability than the bigger ship types (which have a Turn rate of 45° in BFG). The former typically have a Manoeuvrability bonus between 1.5xSpeed up to 3xSpeed; the latter, slower ships tend have a Manoeuvrability bonus between Speed and 2xSpeed. Very slow ships, such as transports and big battleships, are different altogether and should use the examples from the Speed 15 row as guideline.
Speed (BFG) Speed/Manoeuvrability (RT)
15 2 to 4/-20 to -5 (Examples from RT: 2/-20, 3/-10, 4/-5)
20 4 to 6/+0 to +12 (Examples from RT: 4/+4, 5/+5, 5/+8, 5/+12, 6/+10, 6/+12)
25 6 to 8/+13 to +20 (Examples from RT: 7/+15, 7/18, 7/+20, 8/+17, 8/+20)
30 9 to 11/+21 to +30 (Examples from RT: 9/+25, 10/+23, 10/+25, 10/+30, 11/+30)
Detection: Detection has no equivalent in BFG and is therefore harder to estimate. Statistical analysis of existing RT hulls by ship type indicates the following values as baseline (adjust up to 50% up or down):
Grand Cruiser: +10 (+10 is common)
Battlecruiser: +10 (+10 all the way)
Cruiser: +12 (+10 is common)
Light Cruiser: +15 (+15 all the way)
Frigate: +12 (+15 is common)
Raider: +15 (+10 is common but +25 is not unhead of)
Transport: +8 (+5 and +10 are common)
Non-imperial ships should modify the baselines as applicable.
Void Shields: This converts 1:1 from BFG.
Armour: The conversion process of armour is quite straight-forward, although there is some room for interpretation (picking the appropriate value within a given range).
Armour (BFG) Armour (RT)
6 22-24 (or more)
Hull Integrity: Use the following table as rough guideline. You can always adjust up or down by 5 points or so.
Hits (BFG) Hull Integrity (RT)
Consider adding +10 HI per additional Hit beyond that. Or simply use HI = Hitsx10, if Hits > 10.
Morale: Defaults to 100.
Crew Population: Defaults to 100.
Crew Rating: This largely comes down to GM fiat but most imperial ships should be Crack (40). The Gethsemane in Battlefleet Koronus has inexperienced crew and has a Crew Rating of Competent (30). Larger battleships arguably tend to have better crew, so you might want to increase the Crew Rating by one step for most. Non-imperial ships should modify the baseline Crew Rating depending on their background.
Turret Rating: This converts 1:1 from BFG.
Weapon Capacity: Simply add up the weapons for each slot. Consider interpreting batteries with Strength (BFG) > 6 as two seperate batteries.