Decide your use: salads/toppings (needs crisp bite) vs. lettuce cups (needs leaf shape).
Pick the closest substitute from the table by texture: romaine hearts for crisp, butter/Boston for tender cups.
Use the listed ratio: for wetter/softer options, measure by packed leaves so volume stays equivalent.
Adjust prep: trim thick ribs, separate leaves for cups, and keep greens chilled 10–20 minutes for maximum crunch.
Dress and toss at the last minute; if the swap is blander (iceberg), add salt or a sharper dressing to match flavor intensity.