Concrete Mix Ratio Calculator
Determine the exact quantities of cement, sand, and gravel required for any concrete mix. Whether you are ordering ready-mix or mixing on-site, this calculator converts your desired volume into bag counts and tonnage for each material.
Concrete Volume
Mix Design
Mix Results for 27.0 cu ft
Volume Breakdown
How to Calculate Mix Ratios
Concrete mix ratios are expressed as parts of cement to sand to gravel by volume. The ratio determines the final strength and workability of the concrete.
- Determine Total Parts: Add the three numbers in your chosen ratio. For a 1:2:3 mix, total parts = 6.Total Parts = Cement Parts + Sand Parts + Gravel Parts
- Calculate Material Fractions: Each material occupies a fraction of the total volume. Cement = 1/6, Sand = 2/6, Gravel = 3/6.Material Volume = (Material Parts ÷ Total Parts) × Total Concrete Volume
- Convert to Orderable Units: Cement weight = volume × 94 lb/cu ft. Sand and gravel are typically ordered by the cubic yard or ton.
Example Calculation
For 1 cubic yard of 1:2:3 mix using 94lb cement bags:
- Total parts: 1 + 2 + 3 = 6
- Cement: 1/6 × 27 cu ft = 4.5 cu ft → 4.5 × 94 lb = 423 lbs → 5 bags
- Sand: 2/6 × 27 cu ft = 9 cu ft → 9/27 = 0.33 cu yd → ~0.7 tons
- Gravel: 3/6 × 27 cu ft = 13.5 cu ft → 13.5/27 = 0.5 cu yd → ~1.0 tons
- Water: 5 bags × 4.5 gallons = ~22.5 gallons
Common Mix Ratio Mistakes
- Adding too much water: The water-to-cement ratio is the single most important factor in concrete strength. Adding extra water for workability reduces strength by up to 50%. Use a water-reducing admixture instead.
- Using damp sand without adjusting volume: Damp sand bulks up and takes more volume than dry sand. If your sand is wet, increase the measured volume by 15-25% to get the same dry equivalent.
- Confusing weight with volume: Cement is sold by weight (94lb bags) but mixes are specified by volume (parts). A 94lb bag equals about 1 cubic foot of cement volume. Always use volume-based ratios, not weight.
Frequently Asked Questions
What is the best concrete mix ratio?
For general-purpose use (slabs, driveways, sidewalks), 1:2:3 (cement:sand:gravel) is standard. For higher strength like structural columns, use 1:1.5:2. For footings and foundations, 1:3:3 is adequate. Always match the ratio to the application.
How many 94lb bags of cement are in a cubic yard?
For a 1:2:3 mix, one cubic yard of concrete requires approximately 5 bags of 94lb Portland cement. A 94lb bag yields about 1 cubic foot of cement volume. Higher-strength mixes with more cement may require 6-7 bags per cubic yard.
How much water do I add to concrete mix?
Use about 4.5 gallons of clean water per 94lb bag of cement. The ideal water-to-cement ratio is 0.45-0.50 by weight. For hot weather, use cool water to slow the set time. Never exceed 0.60 water-to-cement ratio.