Input parameters
Formula used
Let resin parts be R, hardener parts be H, and additive parts be A. Total parts:
Total parts = R + H + A
For a given total batch amount T (in your chosen unit), the component amounts per batch are:
- Resin amount = T × (R / (R + H + A))
- Hardener amount = T × (H / (R + H + A))
- Additive amount = T × (A / (R + H + A))
Percentage contribution for each component is simply component parts divided by total parts, multiplied by 100.
How to use this fiberglass mixing ratio calculator
- Check the resin system technical data sheet for the recommended mix ratio.
- Decide how much mixed material you want for a single batch.
- Enter the total batch amount and select the matching unit.
- Enter resin and hardener parts as given in the data sheet.
- Optionally add an additive parts value if your system uses thinners or pigments.
- Specify how many batches you plan to mix for the job.
- Press “Calculate component amounts” and copy the resin, hardener, and additive figures.
Example fiberglass mix data table
The table below shows example mixes for typical fiberglass tasks. Use the CSV or PDF export buttons to archive configurations as batch sheets.
| Mix label | Total amount | Unit | Resin parts | Hardener parts | Additive parts | Resin amount | Hardener amount | Additive amount |
|---|---|---|---|---|---|---|---|---|
| General laminating layup | 900 | ml | 2 | 1 | 0 | 600 | 300 | 0 |
| Finishing coat | 1350 | g | 100 | 35 | 0 | 1000 | 350 | 0 |
| Thickened structural repair | 750 | g | 3 | 1 | 0.3 | 523 | 174 | 53 |
Understanding fiberglass mixing ratios
Successful fiberglass laminates depend on an accurate relationship between resin and hardener. The chemical reaction is carefully balanced; small errors change strength, gloss, and durability. This calculator turns abstract mix ratios into clear, repeatable batch recipes for everyday projects, from simple patch repairs to full composite panels and molds.
Weight versus volume based mixing
Manufacturers sometimes quote ratios by weight, sometimes by volume. Scales offer better accuracy; measuring cups are often more convenient onsite. By letting you select a preferred unit, the calculator keeps the underlying ratio correct while adapting to the tools already in your workshop or on the job site.
Configuring multi component resin systems
Many fiberglass systems include resin, hardener, and a thinner, pigment, or filler. Treat each component as a number of parts relative to the total mix. The calculator converts those parts into gram, kilogram, milliliter, or liter amounts, so complex blends stay proportional when you scale batches up or down.
Planning safe batch sizes and pot life
Large resin batches cure faster because heat builds inside the container. Splitting a big layup into several smaller mixes reduces exotherm and gives more working time. By entering a target batch size and the number of batches, you can keep ratios consistent while protecting molds, tools, and finished laminate surfaces from overheating damage.
Coordinating fiberglass with other construction materials
Composite work rarely happens in isolation. Many projects combine fiberglass skins with concrete, mortar, or plaster substrates. You can pair this tool with the Concrete Mix Ratio Calculator and the Cement Plaster Mix Ratio Calculator to keep every layer, from structural base to protective surface, using reliable, documented mix proportions.
Documentation and quality control
Good records make troubleshooting and certification easier. Exporting calculated values as CSV or PDF lets you attach printed batch sheets to workshop orders, inspection reports, or digital project files. Recording resin brand, ratio, temperature, and batch size supports consistent performance across jobs, shifts, and different application crews.
Practical applications in the workshop
The calculator is useful for repairs, fairing, infusion work, small molds, and production layups. Once you know the manufacturer’s ratio, you can confidently scale from tiny test coupons to large hull sections without redoing all the arithmetic. That confidence helps technicians focus on surface preparation, fiber placement, and consolidation quality instead, on every fiberglass mixing job undertaken.
Frequently asked questions
Have the manufacturer’s recommended mixing ratio, the total batch quantity you want to prepare, and your preferred unit. Knowing whether the ratio is specified by weight or volume keeps your results aligned with the technical data sheet.
Yes. Many systems use ratios such as 2.5 to 1 or 100 to 33. Enter the exact parts as decimals if required. The calculator scales each component proportionally so the final mixture still respects the specified ratio.
Mixing by weight is usually more accurate because scales are consistent across temperatures and resin densities. However, many repair shops use marked cups. The calculator supports both approaches, provided you stay consistent with whatever the data sheet recommends.
When you increase the number of batches, the per batch component amounts stay identical, but the total resin, hardener, and additive quantities increase linearly. This helps you plan material purchases while still mixing in small, manageable pots during application.
Yes. There is an optional additive field that can represent thinners, accelerators, pigments, or fillers. When you supply a parts value, the calculator includes it in the total and returns the correct amount, plus updated percentage contribution for each component.
No. The calculator is designed to implement instructions from the technical data sheet, not replace them. Always follow the resin supplier’s official recommendations for safety, cure schedules, compatible additives, and maximum batch sizes, then use the calculator to handle the arithmetic.