FRP density calculator
FRP density is the mass per unit volume of the composite. For pultruded fiberglass profiles, 1.9 g/cm³ (1,900 kg/m³, about 0.0686 lb/in³) is a useful starting assumption. Work density out from the mat, fabric and roving layup or the formulation, turn it into profile weight, or check a weighed sample.
- Estimating density
- 1.9 g/cm³
- Section types
- 8
- Calculation modes
- 4
Use actual dimensions in mm. Ideal sections exclude corner radii, coatings and fittings. For complex profiles, enter the net area from CAD.
Reinforcement layup per meter
Start with the net section above. Add each mat, fabric or veil path and the longitudinal roving groups. The remaining volume is filled by the cured resin / filler matrix.
Surface reference: outer boundary 200.00 mm · inner boundary 160.00 mm.
Surface perimeters are thin-layer approximations. For each actual ply centerline, radiused corner or internal web, choose “Measured developed width” and enter its CAD or shop-floor width. Use separate rows when paths differ.
Layer 1: Outer glass mat
Layer 2: Inner glass mat
Layer 3: Local glass fabric
Coverage applies to the path before overlap. Overlap is the total extra retained width per ply. Factor 1 means one meter of fabric feed per axial meter; use measured consumption for helical or draped feed. A ±45° stitched fabric does not automatically need an angle multiplier: its GSM already includes its fibers. Do not include discarded trim or waste.
Longitudinal roving groups
Use effective density of the cured resin plus retained fillers and additives. For a filled matrix, calculate it separately from its own weight fractions: ρmatrix = 1 / Σ(wi / ρi). Reinforcement densities must include retained binders / stitching, or model these separately.
Density and weight are calculated from retained reinforcement mass and residual matrix volume.
Shaded = net material area · schematic only
Explore the material balance
One meter: 1.6972 kg · density: 1.8858 g/cm³.
Band widths show volume proportions, not physical ply locations. Final results always use the complete material balance.
Drag to calculate
Layup-derived density · volume balance
1.8858 g/cm³
1,886 kg/m³ · 0.0681 lb/in³
Retained reinforcement: 1,170 g/m · 68.9 wt%
Reinforcement volume: 51.2% · voids: 0%
Remaining matrix: 439.4 mm² · 527.2 g/m
Per-layer mass & occupied area
- Outer glass mat: 90 g/m · 35.4 mm² · 200 mm retained width/ply
- Inner glass mat: 72 g/m · 28.3 mm² · 160 mm retained width/ply
- Local glass fabric: 48 g/m · 18.9 mm² · 80 mm retained width/ply
- Roving group 1: 960 g/m · 378 mm²
A positive resin remainder is a volume balance, not proof that the proposed reinforcement can be packed, wetted or pultruded. Verify real layer paths and production data.
1.6972 kg/m
Weight per meter = net area × material density. Changing display units preserves the same profile.
- Net section area
- 900 mm²
- Weight per meter
- 1.6972 kg/m
- Mass per piece
- 10.18 kg
- Total profile mass
- 101.83 kg
Net profile mass only. Packaging, pallets, fasteners, cut waste and manufacturing tolerances are excluded. Sample-derived density is a geometric estimate, not a laboratory test result.
Section inputs and results are carried into the inquiry form. Formulation ingredient details are not included.
How to calculate FRP density and weight
Two quantities, two units
Density (kg/m³) is a property of the material. Linear mass (kg/m) is density multiplied by the net area of the section, so the empty core of a tube contributes no mass.
Step 1
Describe the section
Select the profile shape and enter the outside dimensions and wall thickness in millimeters, or the net area from CAD for a complex section.
Step 2
Enter the material
In layup mode, drag the GSM, roving-end or void sliders and play the fill animation to inspect the volume balance. For weight, enter the material density, piece length and quantity. For density, weigh one bare sample and enter its length.
Step 3
Read density and weight
Read density in g/cm³, kg/m³ and lb/in³, with the net area and profile mass. Send the results with your inquiry to confirm the supply specification.
Formulas
Volume (m³) = area (mm²) × length (m) / 10⁶
Density (kg/m³) = sample mass (kg) / volume (m³)
Linear mass (kg/m) = area (mm²) × density (kg/m³) / 10⁶
Total mass = linear mass × length × quantity
Worked example: 50 × 50 × 5 mm tube
The outside area is 2,500 mm² and the hollow core is 40 × 40 = 1,600 mm², so the net material area is 900 mm². At 1,900 kg/m³ the tube weighs 1.71 kg/m. One 6 m piece weighs 10.26 kg, and ten pieces weigh 102.6 kg before packing. Working backwards, a bare sample weighing 10.26 kg over 6 m with that net area gives an inferred density of 1,900 kg/m³.
These are ideal sharp-corner dimensions. For a pultruded section with radii, use the supplier’s CAD area or published mass per meter. FRP square tubes
From mat GSM and fabric layup to profile density
- Retained width = actual ply path × coverage fraction + total overlap allowance.
- Mat or fabric mass (g/m) = GSM × retained width (mm) / 1,000 × layer count × feed factor.
- Roving mass (g/m) = tex × end count × feed factor / 1,000.
- Reinforcement occupied area (mm²) = Σ[mass (g/m) / constituent density (g/cm³)].
- Matrix area = net area × (1 − void fraction) − reinforcement area.
- Total mass (g/m) = reinforcement mass + matrix area × cured matrix density. Profile density (g/cm³) = total mass / net area.
For a sharp-corner 50 × 50 × 5 mm tube, the outer perimeter is 200 mm, the inner perimeter 160 mm and the net area 900 mm². One 450 g/m² mat on each surface contributes 90 + 72 g/m. An 80 mm-wide 600 g/m² local fabric strip adds 48 g/m, and 400 ends of 2,400 tex roving add 960 g/m. With all reinforcement at 2.54 g/cm³, a 1.20 g/cm³ cured matrix and no voids, the result is 1.6972 kg/m and 1.8858 g/cm³. Surface paths are approximations here; actual ply centerlines refine the result.
For axial feed the consumption factor is 1. For a winding or draping process, use the measured retained fabric area per axial meter; do not multiply a fabric’s GSM again because its fibers run at ±45°. Enter different reinforcement paths as separate rows. The model balances volume; it does not predict compaction, wet-out or manufacturability. EPTA’s raw-material guide describes pultrusion rovings, mats and fabrics.
Calculate FRP density from the laminate formulation
Weight fractions
ρ₀ = 1 / Σ(wᵢ / ρᵢ)
wᵢ is each constituent’s mass fraction (percentage ÷ 100). Do not take an average of densities weighted by mass.
Solid volume fractions
ρ₀ = Σ(vᵢ × ρᵢ)
vᵢ is the fraction of non-void material volume. For a void fraction φ of the final laminate volume, ρ = ρ₀ × (1 − φ), neglecting the mass of the gas.
Example: 50 wt% roving, 10 wt% mat and 10 wt% fabric, all at 2.54 g/cm³, plus 30 wt% cured resin at 1.20 g/cm³. The void-free result is 1.9026 g/cm³; at 2% void volume it becomes 1.8646 g/cm³. Moving the same glass mass between the three forms does not change the calculated density.
Use supplier values for your glass chemistry and cured resin system. Formula accuracy is not measurement accuracy: resin cure, binders, filler loading, moisture and voids all affect real production. CKN explains weight versus volume fractions, and its reinforcement-content guide describes how composition and voids are measured.
Net cross-section area formulas
| Section | Net area A |
|---|---|
| Rectangular tube | BH − (B − 2t)(H − 2t) |
| Round tube | π × t × (D − t) |
| Solid round rod | πD² / 4 |
| Flat bar / plate | B × H |
| L-angle | t × (B + H − t) |
| C-channel / I-beam | 2B × tf + (H − 2tf) × tw |
Density reference and limits
The calculator’s 1.9 g/cm³ default is an estimating assumption, not a certified F1 product value. As a published manufacturer example, Strongwell lists 1.72–1.94 g/cm³ for its Series 500/525 and 625 structural shapes, and its plate ranges differ, which is why the exact product matters. Strongwell’s material property table (PDF)
The tool uses geometric volume, not a displacement test. It does not determine structural capacity, laminate grade or shipping weight. Use the supplier’s datasheet for the final material density and add packaging separately.
Frequently asked questions
What is FRP profile weight per meter?
Weight per meter, also called linear mass, is the mass of one meter of profile in kg/m. It equals net area in mm² multiplied by density in kg/m³ and divided by 1,000,000. This is different from material density. The interactive sliders recalculate both; one 2,400 tex roving end contributes 2.4 g/m before its feed factor.
How do mat GSM, perimeter and layer count determine density?
GSM multiplied by retained developed width in meters, layer count and feed consumption factor gives dry reinforcement grams per axial meter. Divide that mass by constituent density in g/cm³ to get its equivalent occupied area in mm². Add roving area, subtract this and void area from the net section, then fill the remainder with the cured matrix. Total grams per meter divided by net area in mm² gives density in g/cm³.
Which perimeter should I use for each ply?
Use the actual developed ply path. Outer and inner surface perimeters are only thin-layer references. Interior plies, corner radii, local strips, internal webs and multi-cell shapes need their own measured or CAD-developed widths. Layers with different paths should be separate rows. Add retained overlap once and exclude discarded trim.
Can I calculate density from glass roving, mat and fabric content?
Yes. Enter each reinforcement’s percentage and constituent density together with cured resin and fillers. For weight fractions, theoretical density is 1 / Σ(wi / ρi). For non-void volume fractions, it is Σ(vi × ρi). This is a formulation-based prediction; the actual profile may differ due to voids and production variation.
Do glass mat and fabric have a different density from roving?
The same glass chemistry has the same solid density regardless of reinforcement form. Architecture affects packing and resin uptake, so it can change the finished laminate’s glass fraction and voids. Include binders or stitching separately, or use an effective constituent density. Do not enter the apparent bulk density of a loose roll of mat.
What is the density of FRP in kg/m³?
For preliminary estimates of pultruded glass-fiber profiles, this tool uses 1,900 kg/m³ (1.9 g/cm³). A practical estimating range is 1,700–2,100 kg/m³, but FRP is a material family: reinforcement, resin, fillers and voids change density. Confirm the selected laminate’s datasheet value.
Are FRP, GRP and fiberglass density the same?
GRP and GFRP refer to glass-fiber-reinforced polymer, commonly called fiberglass. FRP is broader and also includes carbon- or aramid-reinforced polymers. This calculator’s default is for pultruded glass-fiber profiles; it is not a universal density for every FRP product or for loose glass-wool insulation.
Does a hollow FRP tube have a lower density?
A hollow tube uses less material, so it weighs less than a solid bar with the same outside dimensions and laminate. Its material density is unchanged. Divide mass by the actual material volume, excluding the central opening, when estimating material density.
How do I calculate FRP weight per meter?
Multiply net section area in mm² by density in kg/m³ and divide by 1,000,000. For a 50 × 50 × 5 mm square tube, net area is 900 mm². At 1,900 kg/m³, mass is 1.71 kg/m; one 6 m length is 10.26 kg.
Can density tell me the strength or glass content of a profile?
Density alone cannot establish strength, stiffness, glass content or an EN 13706 grade. Different combinations of resin, glass, fillers and voids can produce similar densities. Use the relevant mechanical and composition test data for the specified laminate.
Is sample mass divided by volume an ASTM density test?
No. This tool estimates density from ideal section geometry and a measured sample mass. Corner radii, dimensional tolerances, coatings and measurement errors affect the result. Laboratory density methods use their specified procedures; request a test report when acceptance depends on measured material density.
Send the section and density with your RFQ
Send the section drawing or dimensions, the laminate or resin requirement, lengths and quantities. We reply within one business day.