Concrete volume and bags with 10% waste
Length×width×thickness in meters → m³. Add 10% waste for formwork and uneven ground. Divide by bag yield 25kg≈0.013m³ 40kg≈0.0208m³.
TL;DR
- Volume = L×W×thick/100 (cm→m)
- Formulas: Vol=L×W×thick/100 | Waste=Vol×1.10 | Bags=Vol/yield
- 4×5 10cm
How it works
Volume = L×W×thick/100 (cm→m). Waste = Vol×1.10. Bags = Vol/wield ceil. 4×5×0.10 →2.0m³ 2.2m³ waste →170×25kg.
The math
2×2×0.15 →0.6m³ 0.66 waste →51×25kg. Always cm/100.
Cannot buy half bag, ceil. Mesh not in volume.
Examples
4×5 10cm
- 2.0m³
- 2.2 waste
- 170×25kg
2×2 15cm
- 0.6m³
- 51×25kg
When to use it
✦ Slab
Order concrete.
✦ DIY
Bags vs ready-mix.
⚠ Common mistakes
- cm not /100
- No waste → short
FAQ (6)
How much is a 25kg bag?
About 0.013 m³ concrete. 40kg ≈0.0208 m³. Check your mix; lightweight varies.
Need rebar?
Slabs over 10 cm or loads need mesh; volume stays same, cost rises.
Are the calculations performed on CalcTracker safe for my privacy?
Yes, all calculations on CalcTracker run exclusively on your local device within the web browser. None of the entered data is sent to external servers or stored remotely. The application is entirely offline-first.
Can I use CalcTracker in offline mode on my smartphone?
Absolutely. CalcTracker is designed as a lightweight, progressive-style web application. Once the page is loaded for the first time, all calculators remain ready to use and fully functional even in the complete absence of an internet connection.
Are the results provided by the calculators accurate for official use?
Our calculators use standard mathematical formulas and verified equations. However, for critical financial, banking, or tax decisions (such as exact car tax or net salary calculations), we always advise consulting with a certified professional or referencing official government portals.
How can I share a specific calculation with someone else?
Simply click the "Share Link" button located in the results panel after performing a calculation. The values entered into the form will be encoded directly into the URL query parameters, allowing anyone who opens the link to see the exact same results instantly.