混凝土计算器 — 估算方量、袋数 & 体积
输入板块或柱子尺寸，即时计算立方英尺、立方码和立方米的混凝土用量，以及所需 60 磅和 80 磅预混合袋数。支持矩形板块和圆形柱子，含常用深度预设。
Concrete Calculator
Estimate volume and bags needed for slabs and columns
常见问题
如何计算浇筑混凝土板需要多少混凝土？
将长度（英尺）× 宽度（英尺）× 深度（英尺）相乘，得到立方英尺。将深度从英寸转换为英尺，除以 12。然后将立方英尺除以 27，得到立方码。10×10 英尺、厚 4 英寸的板：10 × 10 × (4/12) = 33.33 立方英尺 = 1.23 立方码。始终额外增加 5-10% 以应对浪费。
10×10 的混凝土板需要多少袋 80 磅的混凝土？
10×10 英尺、厚 4 英寸的板需要约 33.33 立方英尺的混凝土。每袋 80 磅可覆盖 0.60 立方英尺，因此需要 ceil(33.33 / 0.60) = 56 袋 80 磅混凝土。厚度 6 英寸（50 立方英尺）时，需要 84 袋 80 磅混凝土。
4×4 的柱孔需要多少袋混凝土？
4×4 的立柱通常使用直径 10-12 英寸、深 2-3 英尺的柱孔。对于直径 12 英寸、深 3 英尺的柱：体积 = π × (0.5 英尺)² × 3 英尺 = 2.36 立方英尺。每袋 80 磅约 0.60 立方英尺，需要 4 袋。对于直径 10 英寸、深 3 英尺的柱孔，3 袋 80 磅混凝土即可。
混凝土的立方码和立方英尺有什么区别？
1 立方码等于 27 立方英尺。预拌混凝土以立方码订购和定价，而袋装混凝土按每袋体积销售（60 磅袋：0.45 立方英尺；80 磅袋：0.60 立方英尺）。将立方英尺转换为立方码，除以 27。100 立方英尺等于 3.70 立方码。
20×20 的混凝土板（厚 4 英寸）需要多少立方码？
20×20 英尺、厚 4 英寸的板：体积 = 20 × 20 × (4/12) = 133.33 立方英尺 = 4.94 立方码。加上 10% 浪费：5.43 立方码。需向预拌混凝土供应商订购约 5.5 立方码，或 223 袋 80 磅预混料。超过 1 立方码的浇筑强烈建议使用预拌混凝土。
可以手工搅拌混凝土还是需要搅拌机？
在手推车或桶中手工搅拌，每次处理 3-4 袋（约 2 立方英尺）是可行的。租用电动搅拌机每批可处理 8-10 袋，大大减少体力劳动。对于需要 10 袋以上的大多数项目，建议使用搅拌机。任何超过 1 立方码（约 45 袋 80 磅）的用量，订购预拌混凝土更具成本效益，质量也更均匀。
混凝土需要多长时间凝固？
混凝土在 24-48 小时内初步凝固（可以走人），7 天内达到结构强度（轻载），28 天达到完全设计强度。前 7 天保持混凝土湿润（养护），可防止开裂并确保完全强度。前 72 小时避免重载、冰冻温度和强烈阳光直射。
车道和人行道应使用多少 PSI 的混凝土？
仅有行人通行的人行道、露台和走道使用 3,000 PSI（标准混合物）。车道、车库地板和有车辆通行的区域使用 4,000 PSI。结构基础、挡土墙和商业应用使用 5,000 PSI 或更高。PSI 越高，混凝土越致密、耐用，抗冻融循环能力越强。
Concrete Calculator: Volume, Yards & Bags Guide
This concrete calculator estimates the volume of concrete needed for slabs and columns in cubic feet, cubic yards, and cubic meters. It also calculates how many 60 lb and 80 lb premix bags you need to complete your project.
Concrete Volume Formulas
Slab Formula
For rectangular or square slabs (patios, driveways, floors):
Note: Depth must be converted from inches to feet by dividing by 12.
Column Formula
For circular columns, posts, and piers:
Where r = radius in feet = (diameter in inches / 2) / 12
How to Calculate Concrete for a Slab
- Measure the length and width of your slab in feet.
- Determine the required depth in inches (4" for residential slabs, 6" for driveways, 8" for heavy loads).
- Convert depth to feet: divide inches by 12.
- Multiply length × width × depth (in feet) to get cubic feet.
- Divide cubic feet by 27 to get cubic yards.
- Add 5–10% for waste and spillage.
Depth = 4 / 12 = 0.333 ft
Volume = 10 × 10 × 0.333 = 33.33 ft³ = 1.23 yd³
With 10% waste: 1.35 yd³
Column Volume Formula
Columns use the cylinder volume formula. The diameter is entered in inches for convenience, then converted to feet internally.
Radius = (12 / 2) / 12 = 0.5 ft
Volume = π × 0.5² × 4 = 3.14 ft³ = 0.116 yd³
Common column diameters: 8" (fence posts), 10" (deck piers), 12" (structural columns), 16" (large footings).
Bag Coverage Table
Pre-mixed concrete bags (Quikrete, Sakrete, etc.) are available in 40 lb, 60 lb, and 80 lb sizes. The 60 lb and 80 lb bags are most common for structural work.
| Bag Size | Volume per Bag | Bags per Cubic Foot | Bags per Cubic Yard |
|---|---|---|---|
| 40 lb | 0.30 ft³ | 3.33 | 90 |
| 60 lb | 0.45 ft³ | 2.22 | 60 |
| 80 lb | 0.60 ft³ | 1.67 | 45 |
Recommended Slab Thickness
| Application | Thickness | Notes |
|---|---|---|
| Sidewalk / walkway | 4 inches | Foot traffic only |
| Patio / pool deck | 4 inches | Light outdoor use |
| Residential driveway | 4–6 inches | Passenger vehicles |
| Garage floor | 4–6 inches | Cars and light trucks |
| Shed / workshop floor | 4 inches | Tools, light equipment |
| Commercial / heavy loads | 6–8 inches | Heavy vehicles, forklifts |
Tips for Ordering Concrete
- Add 5–10% waste factor to account for spillage, uneven subgrade, and over-excavation. Use 10% for irregular shapes.
- Minimum ready-mix order is typically 1 cubic yard from most suppliers. For less, use bags or ask about short-load fees.
- Order slightly more rather than less — running short mid-pour creates cold joints that weaken the slab.
- Specify PSI strength: 3,000 PSI for residential slabs, 4,000 PSI for driveways, 5,000 PSI for structural applications.
- Check truck access before ordering — a concrete truck requires about 10 ft width and 12 ft clearance height.
- Have extra hands ready — ready-mix must be placed and finished within 90 minutes of mixing.
Volume Unit Conversions
1 cubic yard (yd³) = 27 cubic feet (ft³)
1 cubic meter (m³) = 35.3147 cubic feet (ft³)
1 cubic meter (m³) = 1.30795 cubic yards (yd³)
1 cubic foot (ft³) = 0.0370370 cubic yards (yd³)
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