FR-4 vs G5
Composite · grade comparison
FR-4 and G5 are both composite grades. FR-4 is the stronger of the two: tensile strength 310 MPa (45 ksi) against 220 MPa (31.9 ksi) for G5, about 41% more. FR-4 is the more ductile: elongation 1.8% versus 1.5% for G5. FR-4 is lighter (1.85 g/cm³ vs 1.95 g/cm³ for G5) and FR-4 is stiffer (22 GPa vs 17 GPa). On the shop floor, FR-4 machines more easily (fair vs poor) and FR-4 sits in a lower cost tier (standard, $$) than G5 (premium, $$$).
FR-4Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
G5Choose it when the part sees heat.
FR-4 vs G5: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all composite grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all composite grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Izod Impact, Notched
Hardness, Rockwell M
Fracture Toughness (K_IC)
Same in both: Compressive Strength 415 MPa60.2 ksi
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Limiting Oxygen Index
Max Service Temperature (short-term)
Heat Deflection Temp. @ 1.8 MPa
Same in both: Specific Heat Capacity 1,100 J/kg·K0.26 BTU/lb·°F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Surface Resistivity
Comparative Tracking Index (CTI)
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Same in both: Polishability 30 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every composite grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | FR-4 | G5 |
|---|---|---|
| Default condition | Epoxy Matrix | Melamine Matrix |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both are offered for CNC machining and Sheet metal. Both take the same 1 finish: Painting.
FR-4 vs G5 — frequently asked
Is FR-4 stronger than G5?
Yes. FR-4 has a typical tensile strength of 310 MPa (45 ksi) against 220 MPa (31.9 ksi) for G5 — about 41% more.
Which is cheaper, FR-4 or G5?
FR-4 is the lower-cost material: it sits in the standard tier ($$) while G5 is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, FR-4 or G5?
FR-4. Its machinability rates fair (45/100) against poor (25/100) for G5.
Ready to make it?
Upload a CAD file and FabDigit prices the part in FR-4 and G5 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.