Resin to Fiberglass Ratio Calculator
Calculate the amount of resin needed for fiberglass reinforcement, estimate total laminate weight, and convert between resin-to-fiber ratio and resin percentage.
Resin / Fiberglass Result
What is the resin to fiberglass ratio?
The resin-to-fiberglass ratio describes how much resin is used relative to the dry weight of fiberglass reinforcement.
$$Resin\ Ratio = \frac{Resin\ Weight} {Fiberglass\ Weight}$$
For example, a ratio of 1.5:1 means 1.5 kg of resin for every 1 kg of dry fiberglass.
How do you calculate resin needed for fiberglass?
$$Resin\ Weight = Fiberglass\ Weight \times Resin:Fiberglass\ Ratio$$
For example, if you have 10 kg of fiberglass and use a 1.5:1 resin ratio:
$$Resin = 10 \times 1.5 = 15\ kg$$
What is the total laminate weight?
Theoretical laminate mass is the sum of the dry reinforcement and resin:
$$Laminate\ Weight = Fiberglass\ Weight + Resin\ Weight$$
With 10 kg of fiberglass and 15 kg of resin:
$$10 + 15 = 25\ kg$$
How much resin should I use for fiberglass?
There is no single resin-to-fiber ratio that works for every laminate. The appropriate ratio depends on the fiberglass type, laminate construction, resin system, consolidation method, and whether the laminate is hand lay-up, vacuum bagged, or manufactured using another process.
Use the resin system and reinforcement manufacturer's recommended process wherever one is available. The ratio entered in this calculator is an estimating target rather than a universal manufacturing specification.
How does resin content affect laminate weight?
Resin content is the percentage of total laminate mass that is resin:
$$Resin\ Content = \frac{Resin} {Resin + Fiberglass} \times 100$$
For a 1.5:1 resin-to-glass ratio:
$$Resin\ Content = \frac{1.5} {1.5 + 1} \times 100 = 60\%$$
What is a good resin to fiberglass ratio?
The answer depends on the laminate process and reinforcement. A manually wet-laid laminate may use considerably more resin than a well-consolidated laminate. Vacuum-assisted processes can generally achieve lower resin content when properly controlled.
Rather than treating one ratio as universally correct, use the manufacturer's target and verify the resulting laminate quality, consolidation, and fiber volume fraction.
Resin to fiberglass ratio chart
This chart shows how the resin fraction changes mathematically with different resin-to-fiber mass ratios.
| Resin : Fiberglass | Resin Content | Fiberglass Content | Total Weight for 10 kg Glass |
|---|---|---|---|
| 0.5 : 1 | 33.3% | 66.7% | 15 kg |
| 0.75 : 1 | 42.9% | 57.1% | 17.5 kg |
| 1.0 : 1 | 50.0% | 50.0% | 20 kg |
| 1.25 : 1 | 55.6% | 44.4% | 22.5 kg |
| 1.5 : 1 | 60.0% | 40.0% | 25 kg |
| 1.75 : 1 | 63.6% | 36.4% | 27.5 kg |
| 2.0 : 1 | 66.7% | 33.3% | 30 kg |
How do you calculate fiberglass from resin?
Rearrange the ratio formula:
$$Fiberglass\ Weight = \frac{Resin\ Weight} {Resin:Fiberglass\ Ratio}$$
For example, 15 kg of resin at a 1.5:1 ratio corresponds to:
$$Fiberglass = \frac{15}{1.5} = 10\ kg$$
Should I add extra resin for waste?
For practical work, an allowance can be useful for resin left in mixing containers, brushes, rollers, spills, trimming, and other losses. The calculator lets you add a percentage waste allowance.
$$Resin_{prepared} = Resin_{required} \times \left( 1 + \frac{Waste}{100} \right)$$
What is fiber volume fraction?
Fiber volume fraction is different from resin-to-fiberglass mass ratio. It describes the proportion of the cured composite volume occupied by fibers and is strongly related to laminate performance.
A mass ratio alone cannot determine fiber volume fraction without considering the densities of the resin and reinforcement.
Can this calculator be used for carbon fiber?
Yes, mathematically the same mass-ratio calculation can be used for carbon fiber, aramid, or other reinforcement. However, the correct processing ratio depends on the reinforcement and resin system.
Resin to fiberglass ratio FAQ
Resin-to-fiberglass ratio = resin weight ÷ dry fiberglass weight. A ratio of 1.5 means 1.5 parts resin for every 1 part fiberglass.
Multiply 1 kg by your target ratio. At a 1.5:1 ratio, you would estimate 1.5 kg of resin per 1 kg of fiberglass.
At a 1.5:1 ratio, approximately 15 kg of resin is required before adding any waste allowance.
It means two parts resin by weight for every one part dry fiberglass by weight.
A 1.5:1 resin-to-fiber mass ratio corresponds mathematically to 60% resin and 40% fiberglass by total laminate mass.
For mass-ratio calculations, yes. Resin-to-fiber ratios are normally expressed as weight ratios unless a particular process specifies otherwise.