---
title: "Concrete Weight: Why 150 lbs/cu ft Matters for Your Slab"
metaTitle: "Concrete Weight 150 lbs/cu ft | SlabCalc"
metaDescription: "Standard concrete weighs 150 lbs per cubic foot. Learn how this affects your slab project, truck capacity, and subgrade support."
h1: "150 LBS PER CUBIC FOOT"
tipType: "key_number"
category: "explainer"
imageUrl: "https://pub-58f2801a058947659dff3bd2681ec614.r2.dev/concrete-weight_01_KEY_NUMBER.png"
imageAlt: "Infographic showing concrete weight by volume: 150 lbs per cubic foot, 4,000 lbs per cubic yard"
sourceGuide: "concrete-weight"
sourceCalculator: "concrete-slab-calculator"
relatedTips:
  - how-much-concrete-pro-secret
  - how-much-concrete-code-requirement
  - how-much-concrete-decision-rule
  - rebar-vs-mesh-vs-fiber-pro-secret
cluster: "tools"
lastUpdated: "2026-03-14"
---

Standard concrete weighs approximately **150 pounds per cubic foot** when cured—or **4,000 pounds per cubic yard**. For a typical 4-inch residential slab, that translates to **50 pounds per square foot**. This single number should guide every decision you make about ordering, transporting, and installing concrete.

## Why This Number Matters

Concrete weight directly impacts three critical project decisions: whether your truck can handle the load, whether your subgrade can support it, and how much labor you'll need. Ignore this number and you risk equipment failure, slab cracking, or worse—a collapsed structure. It's not theoretical; it's structural reality.

## Weight Per Square Foot for Slabs

Most DIYers think in square feet, not cubic yards. Here's the practical breakdown:

- **3-inch slab:** 37 lbs/sqft
- **4-inch slab:** 50 lbs/sqft
- **5-inch slab:** 62 lbs/sqft
- **6-inch slab:** 75 lbs/sqft

A typical 10×12 foot patio at 4 inches thick is 120 square feet. That's **120 × 50 = 6,000 pounds total**. A single cubic yard of concrete weighs 4,000 pounds, so you need 1.5 cubic yards delivered. Your ready-mix truck can handle this—but what about your subgrade?

## Subgrade Matters More Than You Think

Concrete is heavy. If your base isn't compacted properly, that weight will settle unevenly, causing cracks within months. Soil typically compacts to support 3,000–4,500 pounds per square foot. For a 4-inch slab at 50 lbs/sqft, you're fine. But if you're adding a driveway and parking vehicles on it (additional 4,000–5,000 lbs per tire), your subgrade needs proper base preparation—at least 4 inches of compacted gravel, tested with a plate compactor.

## Wet vs. Cured Weight

Freshly mixed concrete from a ready-mix truck weighs **slightly more** than cured concrete because it still contains mixing water. That 4-inch slab weighs roughly 52 lbs/sqft when wet, dropping to 50 lbs/sqft after curing (about 28 days). This 4% difference matters for transport but not for structural design calculations—always use the cured weight.

## When This Number Changes

Lightweight concrete (often used in roofs or specialty applications) weighs only **110–125 lbs/cubic foot**. Reinforced concrete with steel rebar or fiber adds minimal weight—fiber adds maybe 1%, rebar perhaps 2–3% depending on density. High-strength concrete (5,000+ PSI) weighs roughly the same as standard concrete.

## Practical Application: Know Your Load

Before you order, calculate your total load. A 20×20 driveway (400 sqft) at 4 inches thick requires 50 tons of concrete and preparation. Your ready-mix truck holds about 10 cubic yards (40,000 lbs)—so you need 2 deliveries. Each truck weighs 25,000+ pounds itself. Make sure your site access (driveway, gate) can handle a 50,000-pound truck without collapsing.

Understanding concrete weight prevents costly mistakes. Check your subgrade, verify truck access, and plan your labor accordingly. The 150 lbs/cu ft standard is your baseline for everything that follows.