Concrete Mix Ratio Calculator: 1:2:4 & Self-Leveling
Use this free 1:2:4 concrete mix calculator to determine how much sand, gravel and cement is required for mixing on site.
Table of Contents
How much cement, sand, and gravel do I need for a 1:2:4 mix?
For 1 cubic yard of concrete mixed at a 1:2:4 ratio (cement:sand:aggregate), you need about 6 bags of 94 lb cement, 0.59 tons of sand, and 1.25 tons of gravel — plus roughly 34 gallons of water. This ratio produces around 2,200–3,000 PSI concrete, suitable for sidewalks, footings, and general non-structural work. Leveling an uneven floor instead? A 300 sq ft room at ¼” thick needs about 13 bags of self-leveling compound. Enter your own numbers below.
Materials needed
1.00 cu yd wet volume, 1:2:4 ratio
- Dry volume (×1.54)41.6 cu ft
- Water needed34 gal
You need
13 bags
300 sq ft at 1/4″ thick, 50 lb bags
- Total volume6.25 cu ft
- Primer needed1 gal
In this guide
Why mix ratios trip people up
You may have been in this spot: you're mixing your own concrete from separate bags of cement, sand, and gravel instead of buying premix, because it's cheaper for a bigger job. Someone hands you a ratio like 1:2:4 and tells you to go for it. Simple enough — until you realize "1:2:4" doesn't tell you how many bags of anything to actually buy. Is that by weight? By volume? Does the sand shrink once it's wet? How much extra do you need because dry material takes up more space than the wet concrete it becomes?
Get this wrong and you either run short halfway through a pour — the worst possible time — or you way overbuy and end up with half-used bags of sand hardening into a brick in your garage. This calculator turns a mix ratio and your project size directly into bags, tons, and gallons, so you order exactly what the job needs.
How a 1:2:4 mix works
A 1:2:4 ratio means 1 part cement, 2 parts sand, and 4 parts coarse aggregate (gravel or crushed stone), measured by volume. Here's how that turns into an actual shopping list.
The 4-step method
- Find your wet volume. Multiply length × width × thickness for your slab, footing, or fence post base, same as any concrete project.
- Convert to dry volume. Dry ingredients take up about 54% more space than the finished wet concrete, because cement and sand fill the air gaps between aggregate particles. Multiply your wet volume by 1.54 to get the dry volume you actually need to buy.
- Split by ratio. Add up the ratio parts (1+2+4=7 for a 1:2:4 mix). Cement gets 1/7 of the dry volume, sand gets 2/7, and aggregate gets 4/7.
- Convert to bags and tons. A standard 94 lb bag of cement holds about 1 cubic foot. Sand and gravel are usually sold by the ton, so convert cubic feet to weight using typical bulk densities.
All of that math is exactly what the Mix Ratio tab in the calculator above runs automatically — pick your ratio, enter your dimensions, and you'll get bags, tons, and water all in one place.
A worked example
Let's run the numbers for 1 cubic yard of concrete at a 1:2:4 ratio.
Step-by-step
- Wet volume: 1 cu yd = 27 cu ft.
- Dry volume: 27 × 1.54 ≈ 41.6 cu ft.
- Ratio split (1:2:4, 7 total parts): cement = 41.6 ÷ 7 ≈ 5.9 cu ft, sand = 11.9 cu ft, aggregate = 23.8 cu ft.
- Cement bags: 5.9 cu ft ÷ 1 cu ft per 94 lb bag ≈ 6 bags.
- Sand: 11.9 cu ft × ~100 lb/cu ft ÷ 2,000 ≈ 0.59 tons. Aggregate: 23.8 × ~105 ÷ 2,000 ≈ 1.25 tons.
- Water at a 0.5 water-cement ratio: 6 bags × 94 lb × 0.5 ÷ 8.34 lb/gal ≈ 34 gallons.
That matches the commonly cited rule of thumb — about 6 bags of cement per cubic yard for a 1:2:4 mix. Scale it up or down for your actual project volume using the calculator.
Which ratio should you use?
What if your project needs to hold up a driveway instead of just a garden path? Ratio choice matters more than almost anything else in the mix. More cement relative to sand and aggregate means higher strength — and a higher price per yard.
| Ratio | Approx. strength | Best for |
|---|---|---|
| 1:2:4 (M15) | ~2,200 PSI | Sidewalks, garden paths, non-structural slabs |
| 1:2:3 | ~3,000 PSI | Patios, standard driveways |
| 1:1.5:3 (M20) | ~3,600 PSI | Columns, footings, heavier structural work |
Self-leveling floor compound
What if your problem isn't a new pour, but an existing floor that's uneven, pitted, or sloped before new flooring goes down? Self-leveling compound solves that — and it's a completely different calculation than structural concrete, because it's sold and estimated by coverage area at a given depth, not by mix ratio.
A standard 50 lb bag yields about 0.5 cubic feet of material, which covers roughly 48 sq ft at ⅛" thick, 24 sq ft at ¼", or 12 sq ft at ½". Since self-leveler sets in as little as 15–20 minutes, running short mid-pour leaves a visible seam that has to be ground down and redone — so it's worth over-ordering by a bag or two rather than cutting it close.
Switch to the Self-Leveling Floor tab in the calculator above to get your bag count and primer estimate for any room size and pour depth.
Mixing your own concrete or leveling a floor?
Get your exact quantities in the calculator above →Common mistakes to avoid
- ✕Skipping the 1.54 dry-volume factor. Buying only the wet volume in dry materials is the single most common way to run short mid-pour.
- ✕Treating a nominal ratio as a structural spec. 1:2:4 is fine for a garden path, not for a load-bearing column — get an engineer-specified mix for anything structural.
- ✕Adding extra water to make mixing easier. It feels helpful in the moment but directly weakens the final concrete and increases cracking.
- ✕Estimating self-leveler at the wrong depth. Coverage is stated per bag at a specific thickness — plug in your actual pour depth, not a generic bag count, or you'll be short by half your order.
Why trust this guide
Formulas on this page follow the standard ACI 211.1 dry-volume factor (1.54) and commonly cited bulk densities for cement, sand, and aggregate. Self-leveling coverage rates reflect typical 50 lb bag yields across major manufacturers. Always confirm exact bag yield and mix ratio against your specific product's label, and use an engineer-specified design mix for any structural application.
Frequently Asked Questions
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