D20 Mechanic: Tick-Based Initiative

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At the request of an EN World user, I'm working on a modification of the Journey initiative system and porting it to the d20 System.


This modification does a few things differently than standard Journey initiative, which I'll try to outline here.

  • You have to maintain the standard d20 action system; that is, on any given turn, a creature has to be able to take both a standard and a move action. Not doing so causes funky interaction with 5-foot steps, and may also cause some other issues (weird interaction with hustle, for instance).
  • While Dex mod is a reasonable analogue to the Speed trait, there is no readily-apparent analogue to WT. As such, we have to build one.
  • Is ACP useful? Probably not, but it is a thing to keep in mind.

d20 Tick Initiative

Alright, let's get to it.

WT or Bulk

There are two primary methods of determining how much stuff a character carries impacts their initiative. One is WT, and the other is Bulk.

While the mechanical differences between the two are somewhat severe, the end result is relatively the same: the more you carry, the slower you are. In my experience, most characters avoid carrying more than a Light load, though, so Bulk might not have quite the impact desired. On the other hand, WT can be somewhat of a pain to calculate, especially as it must be calculated round-to-round with characters pulling out weapons and shields and dropping items.

The two numbers aren't meant to be used at the same time; essentially, you should determine your level of attention to detail, and pick which to use based on that. WT is more detailed, but also more complicated; Bulk is simpler, but less exact.

Calculate WT

To calculate WT, take the total weight of all equipment carried by the character, and divide by the character's Strength score. Round the result down.

Keep in mind that items the character is actively wielding - like a weapon and/or a shield - halve their weight for purposes of this calculation. In Journey, the weights we deal with are abstractions and a lot smaller, though, so this might not be a reasonable step - it also involves a lot of recalculating.

Always recalculate this number when a characters drops and/or picks up items.

Calculate Bulk

If a character is carrying a Light load, their Bulk is +0. If they are carrying a Medium load, it's +1; and a Heavy load is +2.

The other thing about using Bulk is that calculating action costs of mental actions is now out-of-sync with physical actions. A simple fix might be to take the spell level (or equivalent) and divide by 3, rounding down. Alternatively, if you like the idea of spells taking theoretically more time than physical actions, you could just let it be.


Calculating Speed is easy; just use the Dexterity modifier.


Calculating Acumen is also easy: just use the Intelligence modifier.


Using the standard d20 Initiative roll is alright; it's pretty variable, but the whole of the system is like that anyway, so it's no big deal.

Pick a default initiative, per the Journey initiative rules; we like to use 20, because it's high, but using a higher number in d20 would probably be reasonable, given that folk can reasonably get results higher than 20. 40 should be good, I imagine.

The purpose of the default initiative is to make the math easier. If you want, you can just take whoever has the highest initiative, and set them to tick 0; then, everyone else subtracts their roll from the highest Initiative, and goes in that tick. The end result is the same, but default initiative makes the process a lot faster.

Thought: It might be an interesting idea to apply ACP to Initiative checks. Not sure what the ramifications would be, but it would be interesting to try it out.

Action Costs

Action costs are universal regardless of whether you're using WT or Bulk.

Remember to round down, always, at every step of all calculations. That's how we do these calculations in Journey, and that might be important to maintaining the integrity of the formulas (not sure, though).

Action Costs
  Physical Mental
Action Type Base Cost Speed Weight Acumen Spell Level
Long 16 SPD × 4/5 WT × 4/5 ACU × 4/5 LVL × 4/5
Medium 12 SPD × 3/5 WT × 3/5 ACU × 3/5 LVL × 3/5
Short 8 SPD × 2/5 WT × 2/5 ACU × 2/5 LVL × 2/5
Quick 4 SPD × 1/5 WT × 1/5 ACU × 1/5 LVL × 1/5
Instant 2 SPD × 1/10 WT × 1/10 ACU × 1/10 LVL × 1/10
Free 0 (none) (none) (none) (none)

To find the cost for a given action, take the base cost, subtract the relevant fraction of the character's Speed, and add the relevant fraction of their WT. If a mental action, instead subtract the relevant fraction of their Acumen, and add the relevant fraction of spell level (or its equivalent).

If you're not using WT, ignore that column. Instead, Bulk modifies the action cost type of actions.

To determine the action cost of a d20 action, consult the following table.

d20 Action Type	Tick Init Action Cost
1 Round		Medium (Ongoing)
Full			Medium
Standard		Short
Move			Quick
Attack of Opportunity	Instant
Swift			Instant
Immediate 		Instant
5-Foot Step		Free
Free			Free

When a character finishes their turn, add up the action costs of all their actions taken, and add it to their initiative. They go again in that tick.

If you're using Bulk, the character's Bulk modifier moves each action type up one on the action cost list per point of Bulk (so a character with +1 Bulk taking a Move action calculates that as a Short cost, rather than a Quick).

Ready and Delay

If a character readies, add 20 to their initiative. If the condition of their ready action comes up, set their initiative to that tick + the action cost of their readied action.

If a character delays, deal with that the same way you do in standard d20 initiative.


The important thing to keep in mind, especially for spellcasting, is that the cast doesn't take place over the indicated ticks; in effect, casting is no different than swinging a sword. You take an action, it resolves, and your initiative changes to reflect the actions you took.

The exception to this is (Ongoing) actions, which you are considered to be taking until your next tick comes up.