# Grout Quantity Calculator

Volume, weight, bags and water in one pass.

- Page: https://jianzhujisuan.com/en/grout-quantity
- Category: Concrete (https://jianzhujisuan.com/en/c/concrete)
- Chinese version: https://jianzhujisuan.com/zh/grout-quantity.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Length 1.2 m, Width 0.8 m, Grout thickness 50 mm, Bulk density 2200 kg/m³, Mixing water on dry weight 13%, Over-pour factor 1.05, Bag size 25 kg): **Dry grout required 110.9 kg**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Length | number | 1.2 | m |  |
| Width | number | 0.8 | m |  |
| Grout thickness | number | 50 | mm |  |
| Bulk density | number | 2200 | kg/m³ |  |
| Mixing water on dry weight | number | 13 | % |  |
| Over-pour factor | number | 1.05 | — |  |
| Bag size | number | 25 | kg |  |

## Formula

- **Volume = L × W × T × over-pour**: T in mm, divide by 1000
- **Dry weight = volume × density**: 
- **Water = dry weight × water ratio**: by weight, 1 kg ≈ 1 L
- **Bags = ceil(dry weight ÷ bag size)**: 

## Worked example

Machine base 1.2 × 0.8 m with 50 mm grout and 1.05 over-pour: 0.0504 m³, 110.9 kg of dry grout, so 5 bags of 25 kg (125 kg), 16.3 L of water, 3.25 L per bag.

## Questions

### Why can't grout be watered like ordinary mortar?

Strength, expansion and flow are all designed around one fixed water ratio, working with plasticiser and expansive agent together. Extra water breaks it: strength drops about 8% per 1% of water; expansion becomes uncontrolled and the hardened grout shrinks, leaving voids under the base plate; and bleeding segregates the mix. Weigh the water.

### What thickness should the grout layer be?

Machine base grouting is usually 50-100 mm, never less than 25 mm (thinner cannot be poured or levelled); sleeve grouting uses 15-20 mm cavities. Thickness also depends on anchor bolt embedment and shim height, and must allow the grout to flow under its own weight.

### What about hot weather?

Heat accelerates setting: every 10 ℃ shortens working time by roughly half. Store dry grout and water in the shade, keep water below 20 ℃, mix small batches and place quickly. Never re-temper grout past its working time - the hydrated structure is already damaged and strength will drop sharply.

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