Concrete Calculator
Find how many cubic metres or 25 kg bags of concrete you need in Ireland, and what it will cost.
Measure your project
Your answer
That is about 1.73 cubic yards. We added 10% extra.
If you buy bags
Kilsaran's data sheet: a 25 kg bag of its multi-purpose mix gives about 0.01 m³. A full m³ takes about 100.
If you order a lorry (ready-mix)
Ask for 2.00 m³. We round up to the next 1 m³.
This answer is a guide. For a floor, drive or anything that holds weight, check your local building rules or ask a builder or engineer.
Which costs less?
You also skip mixing 132 bags by hand. Have the edges ready before it comes.
Prices from October 2026, one seller each. Ready-mix: Hanly Quarries, with 13.5% VAT. Bags: B&Q Ireland's shelf price, which we take to include 23% VAT.
Quick answers
- A 4 × 3 m patio, 100 mm thick
- 1.2 m³. With 10% extra, 1.32 m³. That is 132 bags of 25 kg, or 2 m³ of ready-mix.
- Bags in 1 m³
- About 100 bags of 25 kg. Kilsaran says each bag makes about 0.01 m³.
- Which grade?
- C25/30 (30N) or stronger for floors and paths. C28/35 (35N) or stronger for drives and yards. Both from Kilsaran.
- Ready-mix price
- About €143 per m³ for C25/30 (30N), with 13.5% VAT. We found only one supplier that prints a price: Hanly Quarries, for full loads delivered.
- Smallest lorry order
- 1 m³ at Roadstone and Hanly. Hanly sells in whole m³. Under 5–6 m³, expect a small-load charge.
How to work it out
- Measure the length and width in metres.
- Measure the thickness in mm. Divide by 1,000 to get metres.
- Multiply length × width × thickness. This gives cubic metres (m³).
- Add 10% extra for spills and uneven ground.
- For 25 kg bags, divide the m³ by 0.01 and round up. For ready-mix, round up to whole m³.
4 × 3 × 0.1 = 1.2 m³
1.2 + 10% = 1.32 m³
1.32 ÷ 0.01 = 132 bags
Ready-mix: 1.32 m³ → order 2 m³
How to measure and calculate concrete in metres
The formula is length × width × thickness. Put all three in metres and you get cubic metres (m³). That is the unit Irish plants sell in. Thickness is often given in mm, so divide it by 1,000 first.
| Job | m³ (+10%) | 25 kg bags | Lorry order |
|---|---|---|---|
| Patio 4 × 3 m, 100 mm thick | 1.32 | 132 | 2 m³ |
| Patio 6 × 4 m, 100 mm thick | 2.64 | 264 | 3 m³ |
| Trench 10 m long, 600 mm wide, 250 mm deep | 1.65 | 165 | 2 m³ |
| 6 post holes, 300 mm wide, 600 mm deep | 0.28 | 28 | 1 m³ |
Sizes are examples, not advice. A lorry order is rounded up to whole m³, from 1 m³.
Not a rectangle? Split an L-shape into two parts. For a triangle with a square corner, halve one side. Floors and shed bases: see our concrete slab calculator.
Bags, mix your own, or a ready-mix lorry?
Per m³, 25 kg bags at €12.80 cost about 9 times as much as ready-mix. Mixing your own sits in between.
| Way | What you buy | Cost |
|---|---|---|
| 25 kg bags | 100 bags | €1,280 |
| Mix your own (weakest floor mix) | 8+ cement bags, 2 tonne bags | from €210 |
| Ready-mix lorry | 1 m³ | €143 + any small-load charge |
Mix your own uses TGD C's least cement, so a stronger mix costs more. Cement: the middle of 8 prices from 7 sellers. Gravel mix or batch gravel: the middle of 11 sellers. Both with VAT where the seller says so.
Bag and ready-mix prices come from one seller each.
Small loads
- Hanly's price is for a full load of 5 m³ or more, delivered. Below that, it adds a small-load charge.
- Roadstone says a minimum load charge may apply under 6 m³.
- Neither prints the amount, so we start it at €0. Type your quote in "Change prices".
With VAT and no small-load charge, the lorry is cheaper from 12 bags (13 without VAT). For a 1 m³ job, bags only win if the charge tops €1,137.
Concrete mix: making your own with cement and batch gravel
Batch gravel comes in tonne bags with the sand already in it, says Kenny Fuels. You add cement and water.
Cement: for a small plain floor, TGD C allows 1 : 7 cement to aggregate, by volume. It asks for 200 kg of cement per m³ or more (8 bags). That is its weakest mix, 20N.
Kenny Fuels mixes 5 parts batch gravel to 1 of cement, which takes more. No Irish source says how much. For 30N, ask your merchant or order ready-mix.
Batch gravel: our rough estimate, as no Irish supplier gives one. Kilsaran's bagged concrete weighs at least 2,200 kg per m³ once set. We take a site mix as the same.
Take off the cement and up to 170 kg of water. About 1,830 kg is left: 2 tonne bags, or a bit more. Power Aggregates says some bags hold 800–850 kg.
Which grade: 30N or 35N concrete?
Builders say "30N" or "35N". Plants sell by C-class (I.S. EN 206). Roadstone's guide: 30N is C25/30, and 35N is C28/35.
- House floor or path: C25/30 (30N) or stronger, says Kilsaran.
- Drive or outside yard: C28/35 (35N) or stronger, usually brushed for grip (Kilsaran).
- Shed base: no Irish maker names one grade. C25/30 (30N) is our safe pick, from Kilsaran's floor and path lines. Roadstone lists shed bases among its lean-mix uses.
- Fence posts, kerb bedding: a lean mix, about C12/15 (Roadstone, Kilsaran).
| Ask for | C-class | Per m³ |
|---|---|---|
| 25N | C20/25 | €136.20 |
| 30N | C25/30 | €143.01 |
| 35N | C28/35 | €147.10 |
| 37N | C30/37 | €149.82 |
Hanly Quarries, Co. Roscommon, with 13.5% VAT, full loads delivered. One plant only, so ask your own.
For a floor, foundation or drive, check your local building rules or ask a builder or engineer.
Before you ring a ready-mix plant
- Say which grade, such as 30N. Get a delivered price per m³ that includes 13.5% VAT.
- Give your Eircode. Roadstone prices by place, mix and load size.
- Check the lorry can reach: Roadstone's needs 3 m of width and 4 m of height.
- Be ready. On full loads, Roadstone gives the first hour free, then charges €15 per 15 minutes (VAT not stated).
- Don't add water on site. Hanly says that voids its strength promise.
Questions people ask
How much concrete do I need?
Work out the volume: length × width × thickness, with all three in metres. Roadstone suggests adding 5–10% for uneven ground and spills.
How much does one bag of concrete cover?
A 25 kg bag of Kilsaran multi-purpose concrete makes about 0.01 m³. At 100 mm thick, that covers about 0.1 m². So 10 bags cover 1 m².
Is it cheaper to use bags or ready-mix?
Per m³, ready-mix costs far less: about €143, against €1,280 in bags. With VAT and no small-load charge, the lorry wins from 12 bags. Without VAT, from 13.
How much sand and gravel do I need for concrete?
Batch gravel already has the sand in it. For 1 m³, plan on about 2 tonne bags, our rough estimate. Add at least 8 bags of cement, more for a strong mix.
How many bags of cement are in a cubic metre of concrete?
At least 8 bags of 25 kg (200 kg). That is TGD C's least for a plain 20N floor. Stronger mixes need more. So one bag makes at most about 0.125 m³.
How many wheelbarrows of concrete are in a cubic metre?
We found no Irish figure. Heidelberg Materials in the UK says about 35 loads. That is about 29 litres each, so the barrow is only part-filled.
Can I work out concrete in feet or cubic yards?
Yes. Pick "Feet" in the calculator and it shows cubic yards. Irish suppliers sell by the m³, so order in m³. One cubic yard is about 0.765 m³.
Is the VAT on concrete 13.5% or 23%?
Revenue puts ready-mix concrete at 13.5%. It does not list bagged mix. Goodwins' bag prices show 23% VAT. The 5% concrete levy is already in ready-mix prices.
Where our numbers come from
- Concrete per bag: Kilsaran KPRO Multi-Purpose 25 kg data sheet
- 25 kg concrete bag price: B&Q Ireland (Kilsaran, €12.80)
- 20 kg concrete drymix: Goodwins (€8.95; 23% VAT shown)
- Ready-mix prices: Hanly Quarries, Roscommon (€143/m³ C25/30)
- Ready-mix terms: Hanly (1 m³ steps, small load charge may apply)
- Ready-mix full load: Hanly terms (5 m³; small load charge below)
- Ready-mix terms: Roadstone (1 m³ minimum, small-load charge under 6 m³)
- Shed base: Summerhouse24 Ireland guide (10 cm concrete on 10–15 cm gravel)
- VAT on ready-mix concrete: Revenue (reduced rate)
- Irish VAT rates: Revenue (23%, 13.5%, 9%)
- Concrete levy: Revenue (5% on first supply)
- House floor slab rules: TGD C (150 mm concrete, 200 mm hardcore)
- Concrete grades in Ireland: Roadstone guide (35N = C28/35)
- Which concrete grade: Kilsaran (floors C25/30, drives C28/35)
- Cement price: the middle of 8 prices from 7 Irish sellers (25 kg, Oct 2026)
- Tonne bag prices: the middle price from Irish sellers (Oct 2026)
- Batch gravel tonne bag: Kenny Fuels, Wexford (€65 inc VAT, 1,000 kg)
- Gravel cover per tonne: Power Aggregates, Cork (12 m² at 50 mm)
- Full loads, barrows and mixes: Heidelberg Materials UK merchant guide
- Unit sizes: NIST Handbook 44, Appendix C (1 ft = 0.3048 m; 1 US gallon = 231 cubic inches)
Made by BuildersCount. Last checked 4 Oct 2026.
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