Concrete & Masonry

Concrete Bag Calculator

This concrete bag calculator counts the 40, 60 or 80 lb bags for small pours; our concrete installation guide explains when ready-mix is better. For small pours — post holes, stoops, footings for a shed or deck — premixed bags are often the simplest option. Enter dimensions or a volume you already know, and see the bag count for each common size plus the total weight you will be hauling.

Results from this concrete bag calculator are planning estimates; confirm quantities and prices with your supplier or contractor before you order.

Your results will appear here

Enter your measurements and press Calculate. Defaults show a typical example.

How to use the concrete bag calculator

Choose whether you know the dimensions or the volume.
Enter the values and a waste allowance (10% is sensible for hand mixing).
Compare bag sizes — 80 lb bags mean fewer trips; 40 lb bags are easier to lift.

Formula

Bags = volume (ft³) × (1 + waste) ÷ bag yield, rounded up. Yields: 40 lb ≈ 0.30 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³.

Worked example

A 4 × 4 ft landing at 4 in is 5.33 ft³; with 10% waste, 5.87 ft³ → 10 bags of 80 lb (or 14 of 60 lb).

Tips for using the concrete bag calculator

Check the yield printed on the bag; it varies by brand and mix type, and the calculator lets you enter it.
Mixing more than about 20–30 bags by hand is slow and tiring; consider a rented mixer or ready-mix.
Store bags off the ground and covered, because damp bags harden and cannot be used.