{"success":true,"calculator":"concrete","inputs":{"shape":"slab","quantity":1,"length_ft":10,"width_ft":10,"thickness_in":4},"results":{"volume_cubic_feet":33.33,"volume_cubic_yards":1.23,"volume_cubic_meters":0.9439,"bags_80lb":56,"bags_60lb":75},"formula":"Volume (cu yd) = (Length_ft × Width_ft × Thickness_in ÷ 12) ÷ 27","notes":"Add 5-10% extra for waste and spillage."}