FR-4 vs G7
Composite · grade comparison
FR-4 and G7 are both composite grades. FR-4 is the stronger of the two: tensile strength 310 MPa (45 ksi) against 170 MPa (24.7 ksi) for G7, about 82% more. FR-4 is stiffer (22 GPa vs 14 GPa) and G7 runs hotter in service (220°C vs 130°C continuous). On the shop floor, FR-4 machines more easily (45 vs 35 out of 100) and FR-4 sits in a lower cost tier (standard, $$) than G7 (premium, $$$).
FR-4Choose it when strength drives the design, or when the part is machined in volume.
G7Choose it when the part sees heat.
FR-4 vs G7: 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 Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Izod Impact, Notched
Hardness, Rockwell M
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.
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Thermal Conductivity 0.3 W/m·K0.17 BTU/hr·ft·°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
Polishability
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 | G7 |
|---|---|---|
| Default condition | Epoxy Matrix | Silicone 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 G7 — frequently asked
Is FR-4 stronger than G7?
Yes. FR-4 has a typical tensile strength of 310 MPa (45 ksi) against 170 MPa (24.7 ksi) for G7 — about 82% more.
Which is cheaper, FR-4 or G7?
FR-4 is the lower-cost material: it sits in the standard tier ($$) while G7 is premium ($$$). 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 G7?
FR-4, by a small margin. Both rate fair for machinability — 45/100 against 35/100 for G7.
Ready to make it?
Upload a CAD file and FabDigit prices the part in FR-4 and G7 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.