Pick your target texture: soft diced (spreads/salads) vs blended pepper flavor (baking/sauces).
Use the ratio from the list: start at 1:1 for roasted peppers and piquillo; reduce to ¾:1 for raw bell pepper.
Drain very wet jarred ingredients before mixing; if the substitute seems runny, blot and re-chop.
Adjust seasoning to match pimento’s mellow sweetness: add a small pinch of salt for savory dishes or a tiny bit of sugar for overly sharp relishes.
If using for baking, chop small or blend briefly so the pepper flavor disperses evenly.