Grout Quantity Calculator
Volume, weight, bags and water in one pass.
Quick answer
With the default inputs: Length 1.2 · Width 0.8 · Grout thickness 50 etc.Dry grout required 110.9 kg
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Result
Dry grout required
110.9kg
| Volume incl. over-pour | 0.050m³ |
| Bags (whole) | 5bags |
| Dry grout as ordered | 125.0kg |
| Mixing water | 16.3L |
| Slurry volume weight | 141.3kg |
| Water per bag | 3.25L |
Grout must be mixed to the manufacturer water ratio: 1% extra water can cost 8-10% strength, while too little leaves it unable to flow into voids. Meter water by weight; a marked bucket by volume is only valid if you allow for slurry density. Over-pour factor 1.03-1.10, higher with open faces. Use each batch within 30 minutes, 20 in hot weather.
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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) |
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.
How to work it out
- Compute the net volume: length × width × grout depth, dividing by 1,000 when the depth is in mm.
- Apply an overfill factor of 1.05-1.10. Equipment grouting has to flow out of the form and secondary grouting must fill anchor holes, none of which the net volume covers.
- Dry weight = net volume × overfill factor × bulk density. Grouts run 2,100-2,300 kg/m³, with about 5% spread between suppliers.
- Bags = ⌈dry weight ÷ bag size⌉, commonly 25 kg.
- Water = dry weight × water ratio, strictly per the manufacturer; typically 12-14%, and extra water costs strength and causes bleeding.
Where it goes wrong
- Ordering on net volume alone — overflow and anchor-hole filling take 5-10%, so ordering net is always short and topping up mid-pour creates layers.
- Adding water for flow — the water ratio is the balance point between strength and flow; 1% more water loses 5-8% strength and the bleed water leaves a porous layer at the base.
- Mixing too much to use slowly — working life is only 20-30 min, after which flow is gone and forcing it in leaves voids.
Material and cost
High-strength non-shrink grout runs 1,200-2,200 per tonne (rising from C40 to C80); plain cementitious grout 600-900. A cubic metre of secondary grouting is about 2,500-5,000 in material.
On site
- Scabble and clean the base, then pre-soak for 24 h with no standing water, or the grout will give up its water and crack.
- Use a high-level hopper or pressure grouting from one side and let the grout flow, rather than pouring from all sides.
- In winter keep water below 30 °C and materials above 5 °C; cold grout can stay unset for hours.
Basis
- GB/T 50448-2015 Technical code for application of cementitious grout (placing and curing)
- JC/T 986-2018 Cementitious grout (performance requirements)
- GB 50205-2020 Code for acceptance of steel structure construction, Chapter 8 (equipment foundations and secondary grouting)
FAQ
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.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Grout Quantity Calculator. 2026-10-25. https://jianzhujisuan.com/en/grout-quantity
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.