{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"concrete-footing"},"result":{"entity_type":"calculator","id":"concrete-footing","calculator_id":"concrete-footing","canonical_url":"https://tttkmbb.com/construction/concrete-footing","name":"Concrete Footing Calculator","title":"Concrete Footing Calculator – Volume of Strip Footings and Round or Square Piers with Premix Bag Counts","category":"construction","category_name":"Construction & Home","tool_name":"estimate_concrete_footing","featured_mcp_tool":false,"description":"Computes the concrete volume of a strip footing (length × width × depth) or of round or square piers (count × cross-section × depth), adds waste and converts it to cubic yards, cubic feet and bags of premixed concrete using manufacturer yields (80 lb 0.60 ft³, 60 lb 0.45 ft³, 50 lb 0.375 ft³, 25 kg 0.0125 m³, 20 kg 0.010 m³). Planning estimate only.","use_when":"You need the concrete for wall footings, deck or fence post piers, sonotube piers or pad footings, as a ready-mix volume or as a number of bags.","do_not_use_when":"The pour is a flat slab (use concrete-slab), you need cement, sand and aggregate for site-mixed concrete (use concrete-mix-ratio), or the footing size itself must be designed for the soil bearing capacity (engineering, not covered).","inputs":[{"name":"shape","label":"Footing shape","type":"enum","required":false,"default":"strip","values":[{"value":"strip","label":"Strip (continuous) footing","aliases":["continuous","trench","wall footing"]},{"value":"round_pier","label":"Round pier / post hole / sonotube","aliases":["round","cylinder","sonotube","pier"]},{"value":"square_pier","label":"Square pier / pad","aliases":["square","pad"]}],"description":"Strip footing (length × width × depth) or piers (count × cross-section × depth).","example":"strip"},{"name":"unit","label":"Length unit","type":"enum","required":false,"default":"m","values":[{"value":"m","label":"Metres (m)","aliases":["metre","meter","metres","meters","metric"]},{"value":"ft","label":"Feet (ft)","aliases":["feet","foot","imperial"]}],"description":"Unit of the length inputs (m or ft). Use decimal feet for imperial input (18 in = 1.5 ft). Lengths are reported in both units.","example":"m"},{"name":"length","label":"Strip length","type":"number","unit":"m or ft","required":false,"max":10000,"exclusive_min":0,"description":"Total length of the strip footing (m or ft); not used for piers.","example":10},{"name":"width","label":"Width / side","type":"number","unit":"m or ft","required":false,"max":100,"exclusive_min":0,"description":"Width of the strip footing or side length of a square pier (m or ft).","example":0.5},{"name":"depth","label":"Depth / thickness","type":"number","unit":"m or ft","required":true,"max":100,"exclusive_min":0,"description":"Footing thickness or pier depth (m or ft).","example":0.3},{"name":"diameter","label":"Pier diameter","type":"number","unit":"m or ft","required":false,"max":100,"exclusive_min":0,"description":"Diameter of a round pier (m or ft); required for round_pier.","example":0.3},{"name":"count","label":"Count","type":"integer","required":false,"default":1,"min":1,"max":1000,"description":"Number of identical piers (or strip footings).","example":1},{"name":"waste_percent","label":"Waste allowance","type":"number","unit":"%","required":false,"default":10,"min":0,"max":50,"description":"Extra material for cuts, breakage and offcuts, applied as a multiplier (1 + waste_percent/100). Covers over-excavation, uneven trench bottoms and spillage; 10 % is usual for footings dug by hand.","example":10},{"name":"bag_size","label":"Premix bag size","type":"enum","required":false,"default":"80_lb","values":[{"value":"80_lb","label":"80 lb bag (0.60 ft³)","aliases":["80","80lb"]},{"value":"60_lb","label":"60 lb bag (0.45 ft³)","aliases":["60","60lb"]},{"value":"50_lb","label":"50 lb bag (0.375 ft³)","aliases":["50","50lb"]},{"value":"25_kg","label":"25 kg bag (≈ 0.0125 m³)","aliases":["25","25kg"]},{"value":"20_kg","label":"20 kg bag (≈ 0.010 m³)","aliases":["20","20kg"]}],"description":"Bag size used for the bag count, with its typical yield of placed concrete.","example":"80_lb"}],"outputs":[{"name":"volume_m3","label":"Volume","type":"number","unit":"m³","decimals":3,"description":"Concrete volume before waste."},{"name":"volume_ft3","label":"Volume","type":"number","unit":"ft³","decimals":2,"description":"Same volume in cubic feet."},{"name":"volume_yd3","label":"Volume","type":"number","unit":"yd³","decimals":3,"description":"Same volume in cubic yards (1 yd³ = 0.7646 m³)."},{"name":"volume_with_waste_m3","label":"Volume to order","type":"number","unit":"m³","decimals":3,"description":"volume × (1 + waste_percent/100)."},{"name":"volume_with_waste_yd3","label":"Volume to order","type":"number","unit":"yd³","decimals":3,"description":"Volume to order in cubic yards."},{"name":"bags","label":"Bags of premix","type":"integer","decimals":4,"description":"ceil(volume_with_waste / yield per bag)."},{"name":"bag_yield_used","label":"Bag yield used","type":"string","decimals":4,"description":"Bag size and yield assumed for the count."},{"name":"ready_mix_note","label":"Ready-mix or bags","type":"string","decimals":4,"description":"Whether the volume is practical for bagged mix (below about 0.5 m³ / 0.65 yd³) or should be ordered as ready-mix."}],"input_schema":{"type":"object","properties":{"shape":{"description":"Strip footing (length × width × depth) or piers (count × cross-section × depth).","type":"string","enum":["strip","round_pier","square_pier"],"default":"strip","examples":["strip"]},"unit":{"description":"Unit of the length inputs (m or ft). Use decimal feet for imperial input (18 in = 1.5 ft). Lengths are reported in both units.","type":"string","enum":["m","ft"],"default":"m","examples":["m"]},"length":{"description":"Total length of the strip footing (m or ft); not used for piers. Unit: m or ft.","type":"number","maximum":10000,"exclusiveMinimum":0,"examples":[10],"x-unit":"m or ft"},"width":{"description":"Width of the strip footing or side length of a square pier (m or ft). Unit: m or ft.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[0.5],"x-unit":"m or ft"},"depth":{"description":"Footing thickness or pier depth (m or ft). Unit: m or ft.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[0.3],"x-unit":"m or ft"},"diameter":{"description":"Diameter of a round pier (m or ft); required for round_pier. Unit: m or ft.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[0.3],"x-unit":"m or ft"},"count":{"description":"Number of identical piers (or strip footings).","type":"integer","minimum":1,"maximum":1000,"default":1,"examples":[1]},"waste_percent":{"description":"Extra material for cuts, breakage and offcuts, applied as a multiplier (1 + waste_percent/100). Covers over-excavation, uneven trench bottoms and spillage; 10 % is usual for footings dug by hand. Unit: %.","type":"number","minimum":0,"maximum":50,"default":10,"examples":[10],"x-unit":"%"},"bag_size":{"description":"Bag size used for the bag count, with its typical yield of placed concrete.","type":"string","enum":["80_lb","60_lb","50_lb","25_kg","20_kg"],"default":"80_lb","examples":["80_lb"]}},"additionalProperties":false,"required":["depth"]},"output_schema":{"type":"object","properties":{"volume_m3":{"description":"Concrete volume before waste. Unit: m³.","type":"number","x-unit":"m³"},"volume_ft3":{"description":"Same volume in cubic feet. Unit: ft³.","type":"number","x-unit":"ft³"},"volume_yd3":{"description":"Same volume in cubic yards (1 yd³ = 0.7646 m³). Unit: yd³.","type":"number","x-unit":"yd³"},"volume_with_waste_m3":{"description":"volume × (1 + waste_percent/100). Unit: m³.","type":"number","x-unit":"m³"},"volume_with_waste_yd3":{"description":"Volume to order in cubic yards. Unit: yd³.","type":"number","x-unit":"yd³"},"bags":{"description":"ceil(volume_with_waste / yield per bag).","type":"integer"},"bag_yield_used":{"description":"Bag size and yield assumed for the count.","type":"string"},"ready_mix_note":{"description":"Whether the volume is practical for bagged mix (below about 0.5 m³ / 0.65 yd³) or should be ordered as ready-mix.","type":"string"}}},"formula":"strip: volume = length × width × depth × count; round_pier: volume = count × π/4 × diameter² × depth; square_pier: volume = count × width² × depth; with_waste = volume × (1 + waste_percent/100); bags = ceil(with_waste / yield_per_bag), yields 0.60 / 0.45 / 0.375 ft³ for 80 / 60 / 50 lb bags and 0.0125 / 0.010 m³ for 25 / 20 kg bags.","method":"US bag yields follow the QUIKRETE Concrete Mix data sheet and the 25 kg / 20 kg yields are typical manufacturer figures (check the bag: 0.010–0.0125 m³ per 25 kg is common); rebar, formwork, sonotube forms and a gravel bed under the footing are not included. Planning estimate only; check quantities against the supplier's coverage figures and local code before ordering.","sources":[{"name":"QUIKRETE Concrete Mix No. 1101 product data sheet (yield: 80 lb bag 0.60 ft³, 60 lb bag 0.45 ft³)","url":"https://www.quikrete.com/pdfs/data_sheet-concrete%20mix%201101.pdf","type":"reference","retrieved_at":"2026-09-24"},{"name":"QUIKRETE – Concrete, mortar and post-setting calculators","url":"https://www.quikrete.com/calculator/main.asp","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Foundation (engineering)","url":"https://en.wikipedia.org/wiki/Foundation_(engineering)","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"Strip footing 10 m × 0.5 m × 0.3 m, 10 % waste, 25 kg bags","inputs":{"shape":"strip","unit":"m","length":10,"width":0.5,"depth":0.3,"waste_percent":10,"bag_size":"25_kg"},"expected":{"volume_m3":1.5,"volume_ft3":52.97,"volume_yd3":1.962,"volume_with_waste_m3":1.65,"volume_with_waste_yd3":2.158,"bags":132,"bag_yield_used":"25 kg bag, 0.0125 m³"},"url":"https://tttkmbb.com/api/v1/calculate/concrete-footing?shape=strip&unit=m&length=10&width=0.5&depth=0.3&waste_percent=10&bag_size=25_kg"},{"name":"4 round piers 0.3 m diameter × 1 m deep, 10 % waste, 80 lb bags","inputs":{"shape":"round_pier","unit":"m","diameter":0.3,"depth":1,"count":4,"waste_percent":10,"bag_size":"80_lb"},"expected":{"volume_m3":0.283,"volume_yd3":0.37,"volume_with_waste_m3":0.311,"bags":19,"bag_yield_used":"80 lb bag, 0.60 ft³"},"url":"https://tttkmbb.com/api/v1/calculate/concrete-footing?shape=round_pier&unit=m&diameter=0.3&depth=1&count=4&waste_percent=10&bag_size=80_lb"}],"faq":[{"q":"How deep should a footing be?","a":"Below the local frost line and on undisturbed soil; in the IRC, footings are at least 12 in (300 mm) below grade and 6 in (150 mm) thick, with width set by the soil bearing capacity. Check the local code."},{"q":"How many bags for a fence post?","a":"A 10 in (250 mm) hole 2 ft (0.6 m) deep with a 4 × 4 post takes roughly 0.9 ft³ (0.025 m³) of concrete, i.e. two 80 lb bags; enter diameter 0.25 m, depth 0.6 m and the post count."},{"q":"When is ready-mix better than bags?","a":"Above about 0.5 m³ (30 × 80 lb bags) ready-mix is cheaper and gives a consistent strength; most plants have a minimum order (often 1 m³ or 1 yd³) and charge for short loads."}],"tags":["concrete footing calculator","footing volume","pier concrete","sonotube calculator","post hole concrete","bags of concrete"],"related":[{"calculator_id":"concrete-slab","reason":"Slab volume and bags."},{"calculator_id":"cylinder","reason":"Volume of a round pier from radius and height."},{"calculator_id":"rebar","reason":"Reinforcement for the footing or slab."}],"links":{"html":"https://tttkmbb.com/construction/concrete-footing","markdown":"https://tttkmbb.com/construction/concrete-footing.md","json":"https://tttkmbb.com/construction/concrete-footing.json","api":"https://tttkmbb.com/api/v1/calculate/concrete-footing","schema":"https://tttkmbb.com/api/v1/calculators/concrete-footing","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:46:47Z","next_actions":[{"tool":"run_calculator","calculator_id":"concrete-footing","reason":"Run Concrete Footing Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/construction/concrete-footing.md"}}