WEST SYSTEM 105/205 calculator (US)
Calculate 105 Resin and 205 Fast Hardener using WEST SYSTEM’s US recipe. Match the instructions supplied for your market.
5:1 105 Resin:205 Fast Hardener by volumePinned to the US 105/205 technical sheet. Verify the instructions supplied in your market.
How to use this calculator
- Confirm that you have 105 Resin with 205 Fast Hardener and that the linked US technical sheet matches your product.
- Choose your measuring method and starting point, then enter the amount.
- Measure both components on the selected basis. Follow the product’s mixing, temperature and batch-size instructions; this tool does not select a safe pour volume.
Worked example
A 600 mL combined target at 5:1 by volume gives 500 mL 105 Resin + 100 mL 205 Fast Hardener. A 619 g combined target using the US 5.19:1 weight recipe gives 519 g resin + 100 g hardener. These are distinct recipes for distinct measurement methods.
Questions about this calculation
Can I use 5:1 on scales?
The linked US sheet specifies 5.19:1 resin:hardener by weight and 5:1 by volume. Select weight when using scales. Do not apply a volume ratio to mass or use a different market’s weight instructions without checking your exact product documentation.
Does this cover 206, 207 or 209 hardener?
No. This calculator is for the 105/205 pairing. Other hardeners have their own instructions; selecting the correct product is part of establishing the recipe.
I already measured the hardener. Can I calculate the resin?
Yes. Select 205 Fast Hardener already measured. For 20 mL hardener the 5:1 volume recipe calls for 100 mL resin; for 20 g hardener the US weight recipe calls for 103.8 g resin.
Does the total include fillers?
No. The total here is resin + hardener only. Establish and mix that recipe before applying the product instructions for fillers or other additives; filler mass is not hardener mass.
Sources and measurement basis
Use the exact current instructions for your product, version and market. Review date: 16 October 2026.