G: TLDR: Use ¼ teaspoon ground allspice for every 6 whole berries the recipe calls for.

Long form, still concise:

Whole allspice berries are roughly equal to ⅛ teaspoon of ground each.
So if the recipe calls for:

• 3 whole allspice → use ⅜ tsp ground
• 6 whole allspice → use ¼ tsp ground
• 12 whole allspice → use ½ tsp ground

Ground is a little stronger and disperses immediately, so err slightly low if you’re unsure.

Japanese (grade-1 level, simple):
あじ（味） の ちがい は すこし – The flavor difference is small.
こまかい こな（粉） は つよい – Fine powder is strong.

G: Here’s the direct substitution for this exact recipe:

• 4 whole allspice berries → ½ teaspoon ground allspice (level).

Reasoning: whole ≈ ⅛ tsp ground each → 4 × ⅛ = ½ tsp.

If you want it slightly milder (since ground extracts faster), you can do ⅜ tsp, but ½ tsp is the clean, correct equivalent.

Japanese inline (grade-1 simple):
あじ（味） は おなじ – The taste will be the same.
こな（粉） は はやく でる – Powder comes out fast.

G: Got you — you’re saying:

“I don’t want the full ½ tsp. Just bring it up to about ¼ teaspoon. How much ground allspice is that?”

Answer:
Use exactly ¼ teaspoon ground allspice.

That’s the amount you want. It’s half the full substitution, still noticeable, nowhere near overpowering.

Japanese inline:
すこし（少し）だけ つよく なる – It will get only a little stronger.
よんぶんのいち（四分の一） で いい – ¼ is fine.

G: Direct, practical substitution:
Use ½ teaspoon ground cinnamon for each 1 cinnamon stick.

So for your recipe (4 sticks):
→ 2 teaspoons ground cinnamon.

If you want a lighter cinnamon profile (mulled cider can get strong fast), you can safely drop to 1½ teaspoons.

Japanese inline:
こな（粉） は はやく しみる – Powder soaks in faster.
りょう（量） は すくなめ で いい – A smaller amount is fine.