📊 Mix Proportion Chart UK 2026
Complete reference for all UK concrete mix ratios — volumetric proportions, BS 8500 designated mixes, material quantities per m³, water-cement ratios, and Eurocode 2 design properties for every grade from C8/10 to C50/60.
📐 C8/10 → C50/60
✓ BS 8500 / EN 206
🧮 Quantities per m³
🏗️ GEN, RC, PAV, FND, ST
📊 Eurocode 2 Properties
1:2:4
Standard UK domestic mix (C20/25)
0.45–0.65
Typical water-cement ratio range (UK)
BS 8500
UK concrete specification standard (2023 edition)
375 kg
Cement per m³ at 1:2:4 mix (C20/25)
Concrete Mix Proportions by Grade — C10 to C40
Full mix ratios, material quantities per m³, water-cement ratios, and applications for every standard UK concrete grade.
C10 / GEN1
C8/10 — Low Strength, Non-Structural
10 MPa
Mix Ratio
1 : 3 : 6
Cement / m³
220 kg
Sand / m³
660 kg
Aggregate / m³
1,320 kg
Water / m³
~180 L
w/c Ratio
0.82
Slump
S1–S2
Cement Bags
4.4 × 50 kg
Mix Proportion — Relative Volumes (1:3:6)
Cement (1 part)
Sand (3 parts)
Aggregate (6 parts)
Water (w/c 0.82)
Blinding layers
Mass concrete fill
Garden paths
Shed bases (light)
Not for reinforced work
C15 / GEN2
C12/15 — Light Structural
15 MPa
Mix Ratio
1 : 2.5 : 5
Cement / m³
280 kg
Sand / m³
700 kg
Aggregate / m³
1,200 kg
Water / m³
~175 L
w/c Ratio
0.63
Slump
S2–S3
Cement Bags
5.6 × 50 kg
Mix Proportion — Relative Volumes (1:2.5:5)
Cement (1 part)
Sand (2.5 parts)
Aggregate (5 parts)
Water (w/c 0.63)
Strip foundations (house)
Trench fill
Floor slab bedding
Kerb backing
C20 / GEN3
C16/20 — Standard Domestic
20 MPa
Mix Ratio
1 : 2 : 4
Cement / m³
320 kg
Sand / m³
640 kg
Aggregate / m³
1,280 kg
Water / m³
~160 L
w/c Ratio
0.55
Slump
S2–S3
Cement Bags
6.4 × 50 kg
Mix Proportion — Relative Volumes (1:2:4)
Cement (1 part)
Sand (2 parts)
Aggregate (4 parts)
Water (w/c 0.55)
Most common domestic mix
Garden walls
Domestic floor slabs
Retaining walls (light)
Patio base
C25 / RC25
C20/25 — Reinforced Structural
25 MPa
Mix Ratio
1 : 1.5 : 3
Cement / m³
380 kg
Sand / m³
570 kg
Aggregate / m³
1,140 kg
Water / m³
~170 L
w/c Ratio
0.50
Slump
S3
Cement Bags
7.6 × 50 kg
Mix Proportion — Relative Volumes (1:1.5:3)
Cement (1 part)
Sand (1.5 parts)
Aggregate (3 parts)
Water (w/c 0.50)
Driveways (standard)
RC ground slabs
Domestic extensions
Ground beams
Reinforced retaining walls
C30 / RC30
C25/30 — Standard Structural
30 MPa
Mix Ratio
1 : 1 : 2.5
Cement / m³
430 kg
Sand / m³
430 kg
Aggregate / m³
1,075 kg
Water / m³
~172 L
w/c Ratio
0.45
Slump
S3
Cement Bags
8.6 × 50 kg
Mix Proportion — Relative Volumes (1:1:2.5)
Cement (1 part)
Sand (1 part)
Aggregate (2.5 parts)
Water (w/c 0.45)
Beams & columns
Suspended slabs
Roads and highways
Reinforced house foundations
UK new build standard
C35 / RC35
C28/35 — High Strength
35 MPa
Mix Ratio
1 : 1 : 2
Cement / m³
480 kg
Sand / m³
480 kg
Aggregate / m³
960 kg
Water / m³
~163 L
w/c Ratio
0.40
Slump
S3–S4
Cement Bags
9.6 × 50 kg
Mix Proportion — Relative Volumes (1:1:2)
Cement (1 part)
Sand (1 part)
Aggregate (2 parts)
Water (w/c 0.40)
Commercial buildings
Car parks
Bridges (minor)
RC retaining walls
Industrial floors
C40 / RC40
C32/40 — Very High Strength
40 MPa
Mix Ratio
1 : 0.75 : 1.5
Cement / m³
530 kg
Sand / m³
398 kg
Aggregate / m³
795 kg
Water / m³
~185 L
w/c Ratio
0.35
Slump
S4 (plasticiser)
Cement Bags
10.6 × 50 kg
Mix Proportion — Relative Volumes (1:0.75:1.5)
Cement (1 part)
Sand (0.75 parts)
Aggregate (1.5 parts)
Water (w/c 0.35)
Bridges & piles
Prestressed beams
Major infrastructure
Seawater exposure
Nuclear structures
C50 / RC50
C40/50 — Ultra High Strength
50 MPa
Mix Ratio
1 : 0.5 : 1.25
Cement / m³
580 kg
Sand / m³
290 kg
Aggregate / m³
725 kg
Water / m³
~163 L
w/c Ratio
0.28–0.32
Slump
S4–S5 (SP req.)
Cement Bags
11.6 × 50 kg
Mix Proportion — Relative Volumes (1:0.5:1.25)
Cement (1 part)
Sand (0.5 parts)
Aggregate (1.25 parts)
Water (w/c 0.30)
High-rise cores
Long-span prestressed
Offshore structures
Specialist engineer required
Concrete Mix Design Calculator — Quantities per m³ & by Volume
Enter your concrete grade or custom mix ratio, plus the volume required, and get exact cement, sand, aggregate, and water quantities.
Tip: add 5–10% wastage to your calculated volume
Total Volume (with wastage)
—
—
📦 Total Order Quantities
Cement—
Cement (kg total)—
Sand (fine aggregate)—
Sand (25kg bags)—
Coarse aggregate / ballast—
Agg (850kg bulk bags)—
Water required—
📐 Per-m³ Mix Design
Cement per m³—
Sand per m³—
Aggregate per m³—
Water per m³—
w/c ratio—
Mix ratio—
Wet density (approx.)—
📋 Mix Notes
BS 8500 Designated Concrete Mixes — Full UK Reference
All GEN, ST, RC, PAV, and FND designated mixes under BS 8500-1:2023 — the UK complement to BS EN 206. Each designation specifies a performance class rather than a prescription.
🏗️ GEN — General Purpose (Non-Structural)
GEN0 / C8/10
Cube Strength10 MPa
Max w/c0.90
Min Cement180 kg/m³
UsesBlinding, lean fill
Reinforced?No
GEN1 / C12/15
Cube Strength15 MPa
Max w/c0.80
Min Cement210 kg/m³
UsesStrip foundations, trench fill
Reinforced?No
GEN2 / C16/20
Cube Strength20 MPa
Max w/c0.75
Min Cement240 kg/m³
UsesMass concrete, kerb backing
Reinforced?No
GEN3 / C20/25
Cube Strength25 MPa
Max w/c0.70
Min Cement280 kg/m³
UsesGarage floors, paths, general
Reinforced?Limited
| Designation | BS EN Grade | Cyl. / Cube (MPa) | Max w/c | Min Cement (kg/m³) | Max Agg Size | Application | Reinforced? |
|---|---|---|---|---|---|---|---|
| GEN0 | C8/10 | 8 / 10 | 0.90 | 180 | 20mm | Blinding, lean fill, drainage surround | No |
| GEN1 | C12/15 | 12 / 15 | 0.80 | 210 | 20mm | Strip foundations, trench fill, kerbs | No |
| GEN2 | C16/20 | 16 / 20 | 0.75 | 240 | 20mm | Mass concrete, steps, general use | No |
| GEN3 | C20/25 | 20 / 25 | 0.70 | 280 | 20mm | Garage/shed floors, paths, patios | Limited |
🏠 ST — Standardised Prescribed (Site-Specified)
| Designation | Cement (kg/m³) | All-in Agg (kg/m³) | w/c (max) | Approx. Strength | Application |
|---|---|---|---|---|---|
| ST1 | 210 | 1,850 | 0.90 | ~7.5 MPa | Haunching, trench fill — lowest cement |
| ST2 | 240 | 1,850 | 0.85 | ~10 MPa | Mass fill, backing, footings |
| ST3 | 270 | 1,850 | 0.75 | ~15 MPa | Non-structural slabs, driveways |
| ST4 | 300 | 1,800 | 0.70 | ~20 MPa | General purpose, lightly loaded |
| ST5 | 350 | 1,750 | 0.65 | ~25 MPa | Highest standard prescribed mix |
ST1–ST5 Summary (Standardised Prescribed)
ST1210 kg cement — haunching, ~7.5 MPa
ST2240 kg cement — fill, ~10 MPa
ST3270 kg cement — slabs, ~15 MPa
ST4300 kg cement — general, ~20 MPa
ST5350 kg cement — highest ST, ~25 MPa
🏗️ RC — Reinforced Concrete (Structural)
| Designation | BS EN Grade | Cyl. / Cube (MPa) | Max w/c | Min Cement (kg/m³) | Exposure Class | Application |
|---|---|---|---|---|---|---|
| RC20/25 | C16/20 | 20 / 25 | 0.65 | 280 | XC1 | RC slabs — dry, interior |
| RC25/30 | C20/25 | 25 / 30 | 0.60 | 300 | XC2 | RC walls, wet interior |
| RC28/35 | C25/30 | 28 / 35 | 0.55 | 320 | XC3/4 | External RC elements |
| RC32/40 | C28/35 | 32 / 40 | 0.50 | 340 | XC4 | Beams, columns, bridges |
| RC35/45 | C32/40 | 35 / 45 | 0.45 | 360 | XD1 | RC exposed to de-icing salts |
| RC40/50 | C35/45 | 40 / 50 | 0.40 | 380 | XD2/3 | Prestressed, marine exposure |
RC Designated Mixes — Structural Concrete
RC20/25280 kg/m³ | w/c 0.65 | dry interior RC
RC25/30300 kg/m³ | w/c 0.60 | wet interior RC
RC28/35320 kg/m³ | w/c 0.55 | external RC
RC32/40340 kg/m³ | w/c 0.50 | beams & columns
RC35/45360 kg/m³ | w/c 0.45 | de-icing exposure
RC40/50380 kg/m³ | w/c 0.40 | marine / prestressed
🛣️ PAV — Pavement Concrete (Air-Entrained)
PAV1 — Standard Driveways & Footways
BS EN GradeC35/45
Max w/c0.45
Min Cement320 kg/m³
Air Content3.5% (entrained)
UseDomestic driveways, footways
PAV2 — Heavy-Duty Pavements
BS EN GradeC40/50
Max w/c0.40
Min Cement340 kg/m³
Air Content3.5% (entrained)
UseCommercial parking, HGV roads
| Designation | BS EN Grade | Max w/c | Min Cement (kg/m³) | Air Content | Exposure | Application |
|---|---|---|---|---|---|---|
| PAV1 | C35/45 | 0.45 | 320 | 3.5% (entrained) | XF1/3 | Domestic drives, footways, cycle paths |
| PAV2 | C40/50 | 0.40 | 340 | 3.5% (entrained) | XF2/4 + XD | Commercial car parks, de-iced roads, HGV areas |
🌱 FND — Foundation Concrete (Sulphate-Resistant)
| Designation | ACEC Class | Sulphate Class | Min Cement (kg/m³) | Max w/c | Cement Type | Notes |
|---|---|---|---|---|---|---|
| FND2 | AC-1/2 | DS-2 | 280 | 0.65 | CEM I, SRPC, GGBS blend | Slightly aggressive ground conditions |
| FND3 | AC-2 | DS-3 | 320 | 0.55 | SRPC or CEM I+GGBS | Moderate sulphate attack risk |
| FND4A | AC-3 | DS-3/4 | 340 | 0.50 | SRPC or high GGBS blend | Aggressive ground — brownfield sites common |
| FND4B | AC-4 | DS-4/5 | 360 | 0.45 | SRPC + protective measures | Very aggressive — sacrificial layer may be needed |
FND Mixes — Sulphate-Resistant Foundations
FND2280 kg | w/c 0.65 | DS-2 ground
FND3320 kg | w/c 0.55 | DS-3 ground
FND4A340 kg | w/c 0.50 | DS-3/4 aggressive
FND4B360 kg | w/c 0.45 | DS-4/5 very aggressive
NoteGI report required to select FND grade
⚠️ FND Grade Selection Requires a Ground Investigation
You cannot select an FND designated mix without a ground investigation (GI) report confirming the sulphate design class (DS class) of the ground. NHBC Chapter 4.2 and BS EN 8004 require this. Building control will ask for it on any new-build foundation in brownfield or clay-rich ground. Never assume GEN1 is adequate — if sulphates are present, GEN concrete will dissolve.
Eurocode 2 Concrete Design Properties — EN 1992-1-1
Standard characteristic, mean, and design values for compressive strength, tensile strength, and elastic modulus for all normal-weight concrete classes per EC2 Table 3.1.
C12/15
fck,cyl12 MPa
fck,cube15 MPa
fctm1.6 MPa
Ecm27 GPa
εcu33.5‰
UK UseGEN1 / Foundations
C20/25
fck,cyl20 MPa
fck,cube25 MPa
fctm2.2 MPa
Ecm30 GPa
εcu33.5‰
UK UseStandard domestic RC
C25/30
fck,cyl25 MPa
fck,cube30 MPa
fctm2.6 MPa
Ecm31 GPa
εcu33.5‰
UK UseMost common structural UK
C30/37
fck,cyl30 MPa
fck,cube37 MPa
fctm2.9 MPa
Ecm33 GPa
εcu33.5‰
UK UseRC bridges (minor)
C35/45
fck,cyl35 MPa
fck,cube45 MPa
fctm3.2 MPa
Ecm34 GPa
εcu33.5‰
UK UsePrestressed / PAV2
C40/50
fck,cyl40 MPa
fck,cube50 MPa
fctm3.5 MPa
Ecm35 GPa
εcu33.5‰
UK UseBridges & piles
C50/60
fck,cyl50 MPa
fck,cube60 MPa
fctm4.1 MPa
Ecm37 GPa
εcu33.5‰
UK UseUltra high-rise / specialist
| Grade (cyl/cube) | fck,cyl (MPa) | fck,cube (MPa) | fcd (MPa) (γc=1.5) | fctm (MPa) | fctk,0.05 (MPa) | Ecm (GPa) | εcu3 (‰) | UK Designation |
|---|---|---|---|---|---|---|---|---|
| C12/15 | 12 | 15 | 8.0 | 1.57 | 1.10 | 27.0 | 3.5 | GEN1 |
| C16/20 | 16 | 20 | 10.7 | 1.90 | 1.33 | 29.0 | 3.5 | GEN2 / RC20/25 |
| C20/25 | 20 | 25 | 13.3 | 2.21 | 1.55 | 30.0 | 3.5 | GEN3 / RC25/30 |
| C25/30 | 25 | 30 | 16.7 | 2.56 | 1.80 | 31.0 | 3.5 | RC28/35 — most common UK structural |
| C28/35 | 28 | 35 | 18.7 | 2.77 | 1.94 | 32.0 | 3.5 | RC32/40 |
| C30/37 | 30 | 37 | 20.0 | 2.90 | 2.03 | 33.0 | 3.5 | RC35/45 |
| C35/45 | 35 | 45 | 23.3 | 3.21 | 2.25 | 34.0 | 3.5 | PAV1 / RC35/45 |
| C40/50 | 40 | 50 | 26.7 | 3.51 | 2.46 | 35.0 | 3.5 | PAV2 / RC40/50 |
| C45/55 | 45 | 55 | 30.0 | 3.80 | 2.66 | 36.0 | 3.5 | Specialist structural |
| C50/60 | 50 | 60 | 33.3 | 4.07 | 2.85 | 37.0 | 3.5 | High-rise / prestressed |
🔵 Key Eurocode 2 Notation Explained
fck = characteristic compressive strength (MPa) | fcd = fck / γc where γc = 1.5 (design compressive strength) | fctm = mean tensile strength | fctk,0.05 = 5% fractile (lower characteristic) tensile strength | Ecm = mean elastic (Young's) modulus | εcu3 = ultimate compressive strain in parabolic-rectangular stress block = 3.5‰ for grades ≤ C50/60. Note: UK uses cylinder strength (fck) for all Eurocode design — cube strength is for compliance testing only.
Mix Proportion Quick Reference — Click to Copy
The most-used concrete mix ratios in UK construction. Click any card to copy the value to your clipboard.
1 : 3 : 6
C10 — Blinding, paths, lean fill
1 : 2.5 : 5
C15 — Strip foundations, trench fill
1 : 2 : 4
C20 — Standard domestic (most common)
1 : 1.5 : 3
C25 — Driveways, reinforced slabs
1 : 1 : 2.5
C30 — Structural beams & columns
1 : 1 : 2
C35 — Commercial floors, car parks
0.45–0.55
Ideal w/c ratio for structural UK concrete
S1 → S5
BS EN 206 Slump Classes
Water-Cement Ratio — The Most Critical Mix Parameter
The water-cement (w/c) ratio is the single most important variable in concrete mix design. Reducing the w/c ratio increases compressive strength, durability, and impermeability — but reduces workability. All BS 8500 designated mixes specify a maximum w/c ratio.
| w/c Ratio | Approx. 28-day Strength | Slump (unfactored) | Durability | Typical Grade | Notes |
|---|---|---|---|---|---|
| 0.80–0.90 | 10–12 MPa | High (S4–S5) | Poor | C10 / GEN0 | Very workable — blinding, lean fill only |
| 0.65–0.75 | 15–20 MPa | S3 | Moderate | C15–C20 | Standard domestic — most site-mixed |
| 0.55–0.65 | 20–28 MPa | S2–S3 | Good | C20–C28 | General structural — RC foundations |
| 0.45–0.55 | 28–38 MPa | S2–S3 | Very good | C25–C35 | UK standard structural range |
| 0.35–0.45 | 38–50 MPa | S1–S2 (add plasticiser) | Excellent | C35–C50 | Plasticiser essential for workability |
| <0.35 | 50+ MPa | Stiff (superplasticiser) | Exceptional | C50+ | High-performance; specialist design only |
⚠️ Never Add Extra Water to a Ready-Mix Truck on Site
Adding water to a ready-mix truck on site is the single most damaging thing you can do to concrete quality. Every extra litre of water per m³ reduces compressive strength by approximately 1.5–2 MPa. A delivery of C25/30 with 20L/m³ extra water added on site can become equivalent to C20/25 or weaker — failing your building control specification. If workability is insufficient, request a plasticiser-dosed mix from the plant.
Concrete Mix Proportion FAQs — UK 2026
Common questions about UK concrete mix ratios, grades, water-cement ratios, and design standards.
What is the standard concrete mix ratio for foundations in the UK?
Foundation concrete mix ratios in the UK depend on the foundation type and ground conditions:
- Strip foundations (domestic house): GEN1 (C12/15) — 1:3:6 site mix or designated mix from ready-mix supplier
- Trench-fill foundations: GEN1 or GEN2 — 1:2.5:5 to 1:2:4 mix ratio
- Raft foundations: RC25/30 (C20/25) or RC28/35 — 1:1.5:3 to 1:1:2.5 with steel reinforcement
- Sulphate-bearing ground: FND2–FND4 designated mix — do not use GEN or standard RC mixes
- Site-mixed guidance: For a domestic strip foundation, 1 part cement : 2.5 parts sharp sand : 5 parts gravel (1:2.5:5) is widely used by UK builders for GEN1-equivalent strength
- Always confirm with your building control inspector — requirements vary by local authority and ground conditions
What is the difference between C25 and C25/30?
This is a common point of confusion between old UK notation and the current BS EN 206 system:
- C25 = old UK notation — refers to 25 MPa cube strength (150mm cube test)
- C25/30 = current BS EN 206 notation — refers to 25 MPa cylinder strength / 30 MPa cube strength
- The cylinder strength is approximately 80% of the cube strength for normal concretes
- Eurocode 2 design uses the cylinder strength (fck) — so C25/30 in design means fck = 25 MPa
- When ordering from a UK ready-mix supplier, specify the BS EN grade (e.g., C25/30) — the supplier understands this as 30 MPa cube strength
- The old designations (C25, C30, RC30 etc.) are equivalent to the cube strength number in the new notation: old "C30" ≈ new C25/30 in most practical UK contexts
What is ballast concrete and what mix ratio does it use?
Ballast (also called all-in aggregate or combined aggregate) is a pre-blended mix of coarse and fine aggregate sold in 25kg and 850kg bulk bags:
- Ballast concrete uses a 1:6 cement-to-ballast ratio by volume for a C20 equivalent mix
- 1 part cement to 5 parts ballast gives approximately C25 strength
- 1 part cement to 4 parts ballast gives approximately C30 strength
- Ballast concrete avoids the need to separately proportion sand and aggregate — useful for DIY and small site-mixed pours
- Standard 25kg bag coverage at 1:6 ratio and 100mm depth: approximately 0.5 m² per bag of ballast + 1/6 bag of cement
- Ballast contains particles up to 20mm — not suitable for thin sections under 75mm or reinforced sections where 10mm maximum aggregate is specified
What concrete grade do I need for a driveway in the UK?
UK driveways require concrete designed to resist freeze-thaw cycling, deicing salts, and vehicle loading:
- Standard domestic driveway (cars only): PAV1 designated mix (C35/45, air-entrained) — this is the BS 8500 recommended grade
- Heavy-duty driveway (vans, HGVs, forklifts): PAV2 (C40/50, air-entrained)
- Mix ratio equivalent: 1:1:2 to 1:0.75:1.5 (cement : sand : aggregate)
- Minimum thickness: 100mm for cars; 150mm for heavier vehicles, with sub-base compacted beneath
- Air entrainment is mandatory for driveways — it creates microscopic air bubbles that absorb freeze-thaw pressure. Standard non-air-entrained concrete will spall within 2–5 winters when exposed to road salt
- GEN3 (C20/25) is sometimes used for rear domestic drives not subject to salted roads — but PAV1 is strongly recommended for front driveways in the UK climate
How do I convert a mix ratio into kg quantities for a given volume?
Converting a volumetric mix ratio (e.g., 1:2:4) into kg quantities:
- Determine total parts: 1 + 2 + 4 = 7 parts total
- For 1 m³ of concrete: total dry volume ≈ 1.54 m³ (accounts for voids and compaction — cement fills gaps between aggregate)
- Volume of cement = (1/7) × 1.54 = 0.220 m³
- Density of cement = 1,440–1,500 kg/m³ (loose) → 0.220 × 1,500 = 330 kg cement
- Volume of sand = (2/7) × 1.54 = 0.440 m³; sand density ≈ 1,600 kg/m³ → 704 kg sand
- Volume of aggregate = (4/7) × 1.54 = 0.880 m³; agg density ≈ 1,500 kg/m³ → 1,320 kg aggregate
- Water = cement × w/c ratio (e.g., 330 × 0.55 = 182 L)
- The Mix Calculator tab above does all this automatically for any grade or custom ratio