How to Use This Footing Estimate

Quick steps to measure, calculate, and order concrete for this footing.

1. Confirm finished dimensions: 16 in long × 24 in wide × 24 in deep.
2. Convert to feet and compute volume: use 1.3333 ft × 2 ft × 2 ft to get 5.3333 cu ft.
3. Add waste (recommended 10%): 5.3333 cu ft × 1.10 = 5.8666 cu ft for ordering.
4. Decide mix type: choose bagged concrete for small pours or ready-mix if combining multiple footings or pouring continuously.
5. Order quantities: use planning bag counts (20 of 40-lb, 14 of 60-lb, or 10 of 80-lb) or round ready-mix to the nearest practical delivery size.
6. Prepare the hole, compact a subbase, position any reinforcement, and pour, finishing the top to grade.

Formula

The basic formula for a rectangular footing is length × width × depth (all in feet) to get cubic feet. For this footing convert inches to feet first: 16 in = 1.3333 ft, 24 in = 2 ft, depth 24 in = 2 ft.

Area in square feet = length × width = 1.3333 ft × 2 ft = 2.6667 sq ft. Volume in cubic feet = area × depth = 2.6667 sq ft × 2 ft = 5.3333 cu ft.

Convert cubic feet to cubic yards by dividing by 27: 5.3333 cu ft ÷ 27 = 0.1975 cubic yards. To allow for jobsite waste and small measurement errors multiply the cubic feet by 1.10 for a 10% buffer: 5.3333 × 1.10 = 5.8666 cu ft (0.2173 yd³).

Worked Example

Single footing example: one 16"×24"×24" footing requires 5.3333 cubic feet of concrete, which is 0.1975 cubic yards. With a 10% allowance plan on 5.8666 cubic feet (0.2173 cubic yards), which equates to about 20 40-lb bags, 14 60-lb bags, or 10 80-lb bags.

Multiple-footing example: three identical footings (for three deck posts) use 3 × 5.3333 = 15.9999 cubic feet total, which is about 0.5926 cubic yards. With 10% waste plan on 3 × 5.8666 = 17.5998 cubic feet (≈0.6518 yd³) and order about 60 40-lb bags, 42 60-lb bags, or 30 80-lb bags for the group.

Bag Count Estimate

• 10 bags of 80 lb concrete mix
• 14 bags of 60 lb concrete mix
• 20 bags of 40 lb concrete mix

Always verify the actual yield on the product label before buying materials.

When Bagged Concrete vs Ready-Mix Makes Sense

For this small volume a bags-of-concrete approach is usually the most practical: bagged concrete lets you buy only what you need and avoids the minimum-order constraints of many ready-mix plants. Mixing by hand or with a small mixer works well for a single footing.

Ready-mix concrete gives better consistency and is faster for several footings or a continuous pour, but most suppliers have a minimum delivery (commonly around 1 cubic yard). Since this footing including waste is only about 0.2173 cubic yards, ready-mix is rarely cost-effective unless you’re combining multiple pours or topping up other nearby footings.

Common Uses for This Footing Size

A 16x24x24 footing is commonly used for supporting deck posts, pergola posts, fence posts, or small porch columns. Its rectangular shape and dimensions make it practical for single-point supports where the load isn’t too heavy. This size can handle typical residential outdoor structures that need a solid base without taking up much ground space.

Whether this footing size is suitable depends on several factors like the weight it needs to hold, the type of soil, how deep the frost line is in your area, and if reinforcement is necessary. Local building codes may also have specific requirements that affect footing dimensions and installation. It’s important to consider these details before deciding if this footing size will work for your project.

Common Mistakes to Avoid

Common mistakes to avoid when ordering and installing a small footing:

• Mixing up inches and feet when calculating volume.
• Forgetting to add a waste allowance — small jobs still need about 10% extra.
• Ordering ready-mix for a single small footing without checking minimum delivery amounts.
• Failing to check local frost depth, soil bearing, and permit requirements before pouring.
• Not placing required reinforcement or improper placement of rebar/mesh.
• Poor subbase preparation or inadequate compaction beneath the footing.