I'm building a Pulp Scientist in d20 Past, but having some trouble understanding the rules for Inventions (see my other questions).

The Scientist advanced class says, "Inventions tend to be bulky, weighing 10 pounds per level of discovery" (d20 Past p84). Which is fine for the two 1st-level discoveries, but what about the five 0th-level discoveries?

Is there a general rule that when multiplying by zero, one should multiply by one instead? If there is, my poor Scientist's starting inventions will weigh 70 lbs.!

Given the horrendous d20 Modern penalties for being encumbered, I don't really want to sink everything into Strength just to carry my gear.

Does a 0th-level invention weigh zero or ten lbs?

  • 2
    \$\begingroup\$ In D&D 3e (whence d20 Modern and Past comes), 0-level is sometimes treated for construction purposes as ½ level. While I'm unfamiliar with d20 Modern et al., it might be worth seeing if another inventor type (maybe a spellcaster?) uses a similar mechanic. (I know that 5 lbs. per 0-level dingus is still a lot, but at least it's not 10 lbs.!) \$\endgroup\$ Aug 1, 2016 at 15:25
  • \$\begingroup\$ Thanks @HeyICanChan, this is precisely what I was worried about, but I don't know d20 Modern well enough to know if that rule is written anywhere. If you can find one, I would be happy for you to turn your comment into an answer. \$\endgroup\$
    – Mark Booth
    Aug 1, 2016 at 16:05

2 Answers 2


Inventions duplicate Spells from the core book:

Like FX abilities, discoveries come in levels 0-5th...Each discovery duplicates a Mage or Acolyte spell...

There appear to be no rules within the D20 Modern Core or Urban Arcana books regarding using any spell level in a calculation. Magic Item costs, for example, are priced by Caster Level in the FX Section of the core book.

Within other d20 products, such as D&D 3.5, 0-level spells are called out as being half a level for calculations. Thus, Inventions of 0-level discoveries could be considered to be 1/2 (0.5) levels for calculations.

Remember that:

Scientists can further reduce the cost of their inventions by lowering their Scientist level for the purposes of invention construction, but doing so locks the lower Scientist level into the invention.

Which can reduce the weight, if using this half-level ruling.

Without the 'half-level' ruling, and barring any other general rules regarding multiplying by 0, as the level is multiplied in cost, time and weight calculations, 0-level inventions are free, weightless, and take no time to build. Like Macguyver's inventions...

Which may have been intended or not.


10 times 0 is 0. Unless something in the rules says that you round up then they're 0 pounds RAW. This is also supported by the rules as intended, as I can't imagine that the designers would want you to start out carrying 70 pounds of inventions.

  • \$\begingroup\$ Thanks, I know some systems (Warhammer IIRC) have general rules about multipliers to prevent abuse, so I wondered if d20 did also. \$\endgroup\$
    – Mark Booth
    Aug 1, 2016 at 14:55
  • \$\begingroup\$ I'm not particularly familiar with d20 modern, so I could be wrong, but it seems that they intended for the level 0 discoveries to be weightless. Could be kind of interesting to have a scientist lugging around heavy equipment though. Having to set it all down on whatever solid surface you can find when you need to use it. \$\endgroup\$ Aug 1, 2016 at 14:57
  • \$\begingroup\$ This is the problem I'm having @SpaceOstrich, it's looking like I'm going to have to use many of my stat points to boost Strength just to carry my equipment, and the problems will only get worse as the character levels up. A full complement of inventions at 10th level would be 490 lbs! It's a good job I've got a Zeppelin to carry them most of the time, but I can't exactly take that into combat. *8') \$\endgroup\$
    – Mark Booth
    Aug 1, 2016 at 15:30
  • \$\begingroup\$ Yeah. You might be able to use trollies, or other ways of making some of them more portable. Perhaps one of the inventions could be some kind of strength enhancing equipment. \$\endgroup\$ Aug 1, 2016 at 15:30
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    \$\begingroup\$ The "little red wagon with a squeaky wheel". I apologize in advance to any stealth-based characters in your party. Perhaps what you need is some kind of "combined concept" for all the inventions? I dislike to suggest a type of "battlesuit" for any historical concept, but it is the more obvious solution... \$\endgroup\$
    – tzxAzrael
    Aug 1, 2016 at 18:28

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