These calculators provide estimates only. Actual requirements may vary based on site conditions. Always consult qualified professionals before making construction decisions. View full disclaimer.
One cubic yard is 27 cubic feet, and every calculator here starts from that: length times width times depth in feet, divided by 27. The sections below cover the slabs, footings and columns most projects need.
Most residential slabs are 4 inches thick for patios and walkways and 5 to 6 inches for driveways and garage floors. Too thin and the slab cracks under load; too thick and you pay for concrete you do not need.
A 20ft × 20ft driveway, 6 inches thick:
20 × 20 × 0.5 = 200 cubic feet
200 ÷ 27 = 7.4 cubic yards
Order about 10% extra for waste.
Columns carry the weight of a deck, porch or carport down to the footing. Round columns are poured in cardboard tube forms; square ones need site-built forms.
12-inch diameter, 10-foot tall column:
π × (0.5)² × 10 = 7.85 cubic feet
7.85 ÷ 27 = 0.29 cubic yards
Think of footings as the shoes of your building - they spread the weight over a larger area so your structure doesn't sink. The size depends on your soil type and building weight. When in doubt, go bigger - it's much harder to fix a undersized footing than to pour a bit more concrete at the start.
Strip footing: 100ft perimeter, 24" wide, 12" deep:
100 × 2 × 1 = 200 cubic feet
200 ÷ 27 = 7.4 cubic yards
Order 10% extra concrete - it's much cheaper than calling the truck back. For large pours, have a backup plan for excess concrete like a sidewalk extension or extra parking pad.
Never pour in freezing weather or on frozen ground. On hot days, start early in the morning and keep the concrete damp for the first week. If rain is forecast, reschedule: rain on fresh concrete adds water to the surface and weakens it.
Spend time on ground prep - compact that soil, add gravel base for slabs, and use form oil. A few extra hours of prep saves days of fixing problems later.
Don't rush the finish. Wait for bleed water to disappear before finishing. Start curing immediately - concrete needs water to gain strength. Cover with plastic or use a curing compound.
For detailed technical guidance, visit the National Ready Mixed Concrete Association
Look up the three numbers every footing needs — frost depth, snow load, and soil bearing — plus the size charts that follow.
ZIP code lookup, frost depth map, 50-state table with code citations and footing depths for 47 cities.
Ground snow load (pg) by state under ASCE 7-22 and IRC R301.2(5), plus state amendments.
IRC R401.4.1 presumptive values, expansive-soil city watch list, and CA/NC/CO amendments.
IRC R403.1(1) prescriptive footing widths by load and soil bearing.
Deck pier diameter and depth by tributary area under IRC R507 and AWC DCA-6.
Weight per foot for #3 to #18 bars per ASTM A615, plus metric/Canadian sizes.
Diameter, area and weight for #3 to #18, with soft-metric and Canadian equivalents and grade marks.
When you can walk, drive and build on new concrete, and how cold weather changes it.
Avoid these costly errors that ruin DIY concrete projects. Learn what to watch out for before you pour.
Extra water makes mixing easier but weakens concrete by up to 40%. Stick to the recommended ratio for maximum strength.
Concrete needs moisture for 7 days to gain full strength. Letting it dry too fast causes surface cracks and weak spots.
Uncompacted soil settles unevenly, causing cracks. Always compact the base, add gravel, and remove organic material first.
Freezing temps ruin concrete, rain dilutes the mix, and extreme heat causes rapid drying. Check the forecast before you pour.
Concrete shrinks as it cures. Without control joints every 8-10 feet, cracks appear randomly instead of at planned locations.
Get detailed explanations, prevention tips, and expert advice for each mistake.
Read Full ArticleVery accurate! We use the same formulas that ready-mix companies use, plus we automatically add 10% for waste. Our calculations match industry standards to ensure you order the right amount.
For most home projects, standard 3000 PSI concrete works great. We calculate using a 1:1.5:3 ratio (cement:sand:gravel) which gives you strong, durable concrete. Need something special? Just adjust in our material calculator.
Absolutely! Hit the "Export to PDF" button after any calculation. You'll get a professional document with all your measurements - perfect for permits, contractors, or your records.
Driveways and sidewalks usually need wire mesh or fiber. Structural elements like footings and walls need rebar. When in doubt, add reinforcement - it's cheap insurance against cracks.
You can walk on concrete after 24-48 hours. Drive on it after 7 days. Full strength takes 28 days, but it's usable much sooner. Keep it moist the first week for best results.
Don't pour if it's below 40°F or will freeze within 24 hours. Cold slows curing and freezing ruins concrete. In winter, use heated concrete or insulating blankets, or just wait for warmer weather.
