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BRP SIZ-Vehicle scaling


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As some are aware, I've been working on some vehicle write ups and design rules for BRP. One roadblock that I've encountered is that the SIZ scores for large vehicles (over SIZ 100), have been factored down considerably from the SIZ one would expect from the vehicle's mass, displacement, and/or volume.

I'm not complaining. I understand that there are playability reasons why this was done, but it does make figuring out the SIZ scores for large vehicles (mostly ships)a bit more challenging.

I worked out a method for "adjusting" SIZ by tonnage to get SIZ values more in line with the BRP core rules, and was wondering if it looked okay to others, of it if it has some fundemental flaw that I have overlooked. So here it is. Feedback will be appreciated.

SIZ (per SIZ table):Vehicle (Adjusted) SIZ

1-100: AdjSIZ=SIZ

100-600: AdjSIZ=SIZ/20+95

600-2400: AdjSIZ=SIZ/24+100

2000+: AdjSIZ=SIZ/10-40


Dulio-class battleship

Displacement: 22639 long tons = 25356 tons = SIZ 2536 = AdjSIZ 214

Dunkerque-class Fast Battleship

Displacment: 26,500 long tons = 28680 tons =SIZ 2968 = Adj SIZ 257

King George V-class battleship

Displacement: 28,000 long tons = 31360 tons = SIZ 3136 = AdjSIZ 274


Displacement: 41675 long tons = 46676 tons = SIZ 4668 = AdjSIZ 427

Forrestal-class CV (CVA-59)

Displacement: 60,000 long tons = 67200 tons = SIZ 6720 = Adj SIZ 632

Enterprise (CVAN-65)

Displacement: 75700 long tons = 84784 tons = SIZ 8478 = AdjSIZ 808

Nimitz (CVN-68)

Displacement: 81600 long tons = 91392 tons = SIZ 9139 = AdjSIZ 874

Southampton-class cruiser

Displacement: 9100 long tons = 10192 tons = SIZ 1019 = Adj SIZ 142

Swiftsure-class submarine

Displacement: 11195 long tons (submerged) = 12538 tons = SIZ 1254 =AdjSIZ 152

Los Angeles-class Submarine

Displacement: 26100 long tons (submerged) = 29232 tons = SIZ 2923 = ADjSIZ 222

Carnival Miracle-Cruise Ship

Displacement: 85900 long tons = 96208 tons = SIZ 9621 = Adj SIZ 922

Vosper Thornycroft Mk9

Displacement: 850 long tons = 952 tons - SIZ 209 = ADj SIZ 115

Chaos stalks my world, but she's a big girl and can take of herself.

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<scratches head>It looks like you have things figured out with regards to SIZ as on the revised table. They are 4 figure values, but if accurate then whey create something else to make it "look better"? </scratches head>


Part of the difficulty lies in the fact that naval tonnage is usually expressed in long tons (2240 pounds) rather than short tons (2000 pounds). So it adds in another step. This conversion could be combined into the SIZ calaculation by diding displacement by 11.2 instead of 10, but I wanted to show each step so people wouldn't wonder why I didn't just divide the tonnage by 10.

Note that snce a mertric ton (1000kg) is approximately 2200 pounds, we could get away with using long tons as metric tons and be within 2%. But 2% can mean a difference 1000 SIZ/Hit Points for something like an Iowa-class battleship.

What I'll do for VEHICLES will be to give a table where you can look up vehicle SIZ and SIZ by tonnage. SO it will be just one step. Currently, I have a spreadsheet do all the work, and just spit out the game numbers.

I'd rather see a new improved SIZ table that doesn't break above SIZ 100, even if it's not in line with the BRP rules. Your calculations seem to work well fixing the table, but I would prefer a table that was fixed allready, at least with only one new method of conversion when it passes the 100 mark.


So would I. but I'm trying to get everything to fit with the core book, rahter that rewiting everything from scratch. That way people can just grab stats and go with it.

In my opinion, the SIZ table (orginal or revised) isn't the problem so much as the vehicle SIZ ratings. The SIZ table is for the most part, the same as the one in the BRP book, and is similar to the ones used in CoC and even RQ3.

I'm tempted to just use the full SIZ value, it would work out better for a lot of things. Most ships can taker quite a few hits before "running out of hit points". But with the way BRP works, and with battleships having around 36 points of armor, hit points (and weapon damaged), need to to be scaled down to match. For example, with cannon doing 4D8+8 and a "saling ship" having 10AP and 96 hit points, one broadside is going to be far more effective in BRP that it probably should be.

I'm not sure if using a "scaled down" SIZ table for everything would be any improvement. The gap between a tank SIZ 90ish/60mt and a Battleship (SIZ 240, approximately 28,000 tons), squeezes about 24,000 tons into the SIZ100-200 range. This squeezes eventhing from a 100 ton sloop up to a 20,000 ton battlecruiser into about a 100 point SIZ range. Conversly, the ratio between the battleship and carrier (SIZ 640) looks almost linear.

While this isn't great for vehicles,I suspect it worse when used for other things.

I'm open to sugesstions.

Chaos stalks my world, but she's a big girl and can take of herself.

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