Concrete Bag Calculator
Convert a known project volume into whole bags using the yield printed for the exact concrete mix and package size.
- Required project volume
- 10 ft³ (0.37 yd³)
- Volume with allowance
- 10.5 ft³ (0.39 yd³)
- Purchased bag yield
- 10.8 ft³ (0.4 yd³)
- Total dry mix weight
- 1,440 lb
- Excess after rounding
- 0.3 ft³ (0.01 yd³)
Bag weight does not determine yield. Enter the yield printed for the exact concrete mix and bag size you will buy.
Show calculation
10 ft³ × (1 + 5%) ÷ 0.6 ft³/bag = 18 whole bagsTransparent method and editable product assumptions. Verify current labels and project requirements.
How this calculator works
Start with a required concrete volume in cubic feet or cubic meters. It may come from a slab, step, post-hole, footing, repair, or another shape calculated from an approved plan.
The concrete bag calculator applies one allowance to net volume, divides by the editable yield per bag, and rounds the fractional result up. Purchased yield and rounding excess stay visible so a whole-bag result can be audited.
QUIKRETE publishes approximate Concrete Mix yields of 0.30 ft³ for 40 lb, 0.375 ft³ for 50 lb, 0.45 ft³ for 60 lb, 0.60 ft³ for 80 lb, and 0.675 ft³ for 90 lb bags. These are reference examples for that product line, not a rule that transfers to every mix.
Formula
Whole bags = ceil[required volume × (1 + allowance) ÷ product yield per bag]The live substitution appears with your result.Control example: 10 ft³ required volume
Ten cubic feet with 5% allowance creates an order volume of 10.5 ft³.
At 0.60 ft³ per 80 lb bag, 10.5 ÷ 0.60 = 17.5, so buy 18 bags. Purchased yield is 10.8 ft³.
Assumptions and limits
- Required volume is already calculated from the correct project geometry.
- Bag yield matches the exact product and consistency.
- Allowance is applied once before package rounding.
- Total dry weight is a handling reference, not mixed or cured concrete weight.
Common measuring mistakes
- Selecting yield from bag weight alone without reading the product data.
- Entering cubic yards as cubic feet.
- Rounding project volume before dividing by yield.
- Using both a geometry calculator’s waste allowance and another allowance here.
Sources
Product-specific values remain editable. These sources support the method and stated examples; they are not a universal substitute for your supplier’s current label.
- QUIKRETE Concrete Mix data sheet Publishes approximate yield for 40, 50, 60, 80, and 90 lb Concrete Mix bags.
- QUIKRETE Concrete Calculator Confirms that bag estimates use approximate product yields and do not automatically include uneven substrate or waste.
Questions people ask
How many bags of concrete do I need?
Multiply net volume by one allowance, divide by the exact product yield per bag, and round up to a whole bag.
How much does an 80 lb bag of concrete cover?
The referenced QUIKRETE Concrete Mix data sheet lists approximately 0.60 ft³ per 80 lb bag. Other mixes can differ.
Can I enter cubic yards?
In US mode enter cubic feet; one cubic yard equals 27 cubic feet. In metric mode the input switches to cubic meters.
Why are bag weight and yield separate?
Weight describes dry package mass. Yield describes mixed volume and is the number needed for quantity.
Should I round each section separately?
Combine compatible project volumes before final package rounding when they use the same mix and allowance. Separate orders when products or placement requirements differ.