Scenario
20x20 flat slab, 4 in
- Reponse rapide
- 5.43 yd3 / 245 80-lb bags
- Verification de materiau
- $1,045.95 ready-mix material screen
- Ecran installe
- $3,200-$7,200 at $8-$18/sq ft
- Verification suivante
- Confirm access, crew timing, finish, and joints.
Garage Fondation Beton Estimateur
Garage Slab Calculator: 20x20 and 24x24 Yards, Bags, Cost, and Quote Check
Estimate garage slab concrete from length, width, thickness, waste factor, and bag yield. Then compare the 20x20 and 24x24 material-only cost screens before deciding whether the answer belongs in a bag pickup plan, a ready-mix order, or a written contractor quote review.
Author: Concrete Estimator Hub estimating deskUpdated July 29, 2026Sources: QUIKRETE, Sakrete, NRMCA
Point de contrôle de devis de garage
Use the calculator answer as the material baseline, then reject apples-to-oranges bids until vapor barrier, base prep, reinforcement, joints, apron, edge detail, finish, cleanup, permits, and inspection responsibility are visible.
| Ligne de devis | Estimation rapide | Quoi verifier |
|---|---|---|
| 20x20 garage slab | 5.43 yd3 / 245 80-lb bags | Ready-mix, crew timing, and finish plan should be named. |
| 24x24 garage slab | 7.82 yd3 / 352 80-lb bags | Ask for delivery, access, waiting time, and short-load rules. |
| Vapor barrier | Scope line required | Do not assume moisture control is included in a slab price. |
| Reinforcement and joints | Layout required | Compare rebar, mesh, fiber, chairs, saw cuts, and curing timing. |
| Apron and edge detail | Separate quantity | Slope, threshold, thickened edge, and finish can change the bid. |
Pont de coût de dalle de garage
Separate material-only cost from installed garage scope
These screens use $165 per yd3 plus a $150 delivery placeholder for ready-mix material. They make contractor bids easier to compare, but the written local quote still controls the final scope.
Scenario
24x24 flat slab, 4 in
- Reponse rapide
- 7.82 yd3 / 352 80-lb bags
- Verification de materiau
- $1,440.30 ready-mix material screen
- Ecran installe
- $4,608-$10,368 at $8-$18/sq ft
- Verification suivante
- Treat bags as a warning; compare written ready-mix bids.
Scenario
24x24 with 12 in thickened edge
- Reponse rapide
- 10.43 yd3 / about 470 80-lb bags
- Verification de materiau
- $1,870.95 material-only edge screen
- Ecran installe
- Needs separate edge, forms, and inspection scope
- Verification suivante
- Do not compare this against a flat-slab calculator result.
Enter Garage Slab Size
Resultats
Estimation en directReponse first
A 20x20 garage slab at 4 in with 10% waste needs about 5.43 yd3, roughly 245 common 80 lb bags, or about $1,045.95 on the ready-mix material screen. A 24x24 slab needs about 7.82 yd3, 352 common 80 lb bags, and about $1,440.30 before labor, thickened edges, vapor barrier, base prep, reinforcement, apron, finish, permits, and inspection scope.
Reponse rapide
Convertir le numero de dalle de garage en prochaine etape d achat
The differentiator is not only cubic yards. Use the result to choose the right workflow before ordering concrete or approving a garage slab bid.
Signal de résultat
Under 75 80-lb bags
Build a shopping list and confirm pickup weight before buying.
Creer la liste d achatSignal de résultat
150+ bags or one continuous garage floor
Price ready-mix, delivery, unload time, and short-load exposure.
Comparer ready-mixSignal de résultat
Any contractor garage slab bid
Check thickness, vapor barrier, base prep, reinforcement, joints, apron, edge detail, finish, permits, cleanup, and inspection.
Review quote scopeGarage slab bid scope
Turn garage slab yards into a quote-ready checklist
Most garage slab calculators stop at cubic yards and bag counts. This scope layer keeps that math, then flags the details that usually change a garage bid: vapor barrier, thickened edge, reinforcement, apron, saw cuts, inspection, delivery access, and cleanup.
Garage area
400 sq ft
Buying signal
Ready-mix planning signal
Scope score
33/100
| Scope check | Why it matters |
|---|---|
| Finished garage floor dimensions are separated from apron and stem-wall work. | Aprons, stem walls, and flat slab areas often belong in separate bid lines. |
| Subgrade, gravel base, compaction, drainage, and vapor barrier are specified. | Moisture control and base work are common hidden garage slab exclusions. |
| Thickened edge, turndown, reinforcement, and vehicle-load assumptions are written into the scope. | Load assumptions make bids comparable beyond a simple yardage total. |
| Control joints, saw-cut timing, finish, curing, threshold slope, and cleanup are assigned. | Garage doors need drainage, finish, and joint details before the pour. |
| Truck access, chute reach, washout, pump or buggy placement, and unload time are priced before dispatch. | Access and unload time can move cost from material to delivery labor. |
| Two-car or larger garages are checked for pour sequence and joint panel layout. | Larger slabs need joint panel planning and sometimes staged placement. |
| Ready-mix minimums, short-load fees, returned concrete, and inspection timing are checked. | This turns the calculator answer into a quote-review question. |
Sources and checks
Piste de citations pour la calculatrice de dalle de garage
The calculator uses common planning yields and a simple slab formula. Confirm the product label, ready-mix quote, and written garage scope before buying or approving work.
| Controle | Source | Comment c est utilise |
|---|---|---|
| Bag yield and coverage | Cross-checks the common 40/60/80 lb bag-yield assumptions behind the garage slab bag counts. | |
| Ready-mix and placement context | Supports treating 200+ bags as a delivery, access, placement, and quote-scope warning. | |
| Concrete material background | Keeps the material estimate grounded while this page avoids structural engineering claims. | |
| Garage quote scope | Separates vapor barrier, reinforcement, joints, apron, base prep, finish, cleanup, and inspection from material-only yardage. |
Concrete Estimator Hub is independent and is not affiliated with these manufacturers, suppliers, retailers, or industry groups.
Formule de dalle de garage
Surface de dalle
Area = garage slab length x garage slab widthArea = 20 x 20 = 400.00 sq ftVolume de beton
Volume = length x width x thicknessVolume = 20 x 20 x 0.333Marge et sacs
Final volume = 133.3333 x (1 + 10%/100)Bags = ceil(final volume / 0.6)Yards et sacs pour dalle de garage
| Dalle de garage | Epaisseur | Beton avec 10% de gaspillage | 40 lb bags | 60 lb bags | Sacs de 80 lb |
|---|---|---|---|---|---|
| 20 x 20 ft | 4 in | 5.43 yd3 | 489 | 326 | 245 |
| 24 x 24 ft | 4 in | 7.82 yd3 | 704 | 470 | 352 |
| 24 x 24 ft | 5 in | 9.78 yd3 | 881 | 587 | 441 |
| 30 x 30 ft | 4 in | 12.22 yd3 | 1100 | 734 | 550 |
These bag counts use common bag yields and are meant to show why full garage slabs usually need ready-mix planning. Use the calculator above for your exact slab size, thickness, and waste.
Exemples d estimations de dalle de garage
Garage Portee Items to Keep Separate
| Élément | Verification d estimation | Pourquoi |
|---|---|---|
| Main garage floor | Length x width x slab thickness. | Core cubic yards and material-only cost. |
| Thickened edge | Perimeter length x added width x added depth. | Adds concrete, forms, and reinforcement scope. |
| Garage apron | Separate slab area outside the garage door. | Often has different slope, finish, and joint details. |
| Footings or stem wall | Use footing dimensions instead of slab thickness. | Structural and frost-depth rules may apply. |
Avant You Comparer Deviss
- Confirm finished formed dimensions before ordering.
- Run both 4 in and 5 in thickness if the design is not final.
- Keep apron, thickened edges, and footings as separate sections.
- Ask whether vapor barrier, reinforcement, joints, permits, and inspection are included.
Notes de planification de dalle de garage
A garage slab calculator estimates material quantity. It does not approve the slab design, vapor barrier detail, reinforcement, frost-depth requirement, drainage slope, or inspection scope.
For the full written guide, see the guide de calculatrice de dalle de garage beton. For thickness assumptions, use the concrete slab thickness guide. If the garage includes a footing or stem wall, estimate that separately with the concrete footing calculator.
Questions frequentes
Avertissement: Cette calculatrice sert seulement a planifier le materiau beton. Conditions du site, preparation de base, renfort, drainage, joints, precision des coffrages et regles locales peuvent changer les besoins reels. Consultez un entrepreneur ou ingenieur qualifie pour le structurel.