Epoxy resin calculator
This epoxy resin calculator works out how much resin you need for a surface or a mold, and how to split it into resin (part A) and hardener (part B). A 48 × 24 in tabletop coated 1/8 in thick needs 79.8 fl oz of mixed epoxy, or 87.8 fl oz with 10 % extra – about 6.75 lb. Enter the mix ratio from your product label, by volume or by weight.
How it is calculated
Epoxy volume = area × thickness. In inches: length × width × thickness gives cubic inches; 1 in³ = 16.387 ml = 0.554 fl oz. Weight = volume × density. Then split the mixed amount by the ratio on the label: with 1 : 1 half resin, half hardener; with 5 : 1 five parts resin to one part hardener.
Epoxy resin chart (1/8 in coat)
| Surface | Epoxy | With 10 % extra |
|---|---|---|
| 12 × 12 in | 9.97 fl oz | 11 fl oz |
| 24 × 24 in | 39.9 fl oz | 43.9 fl oz |
| 48 × 24 in | 79.8 fl oz | 87.8 fl oz (0.69 gal) |
Why the ratio type matters: WEST SYSTEM gives its 105 resin with 205 hardener as 5 : 1 by volume but 5.19 : 1 by weight, because resin and hardener have different densities. The cured epoxy has a specific gravity of 1.18 – that is the default density here. Use the values on your own product’s data sheet; casting and art resins differ.
Examples
- Tabletop 48 × 24 in, 1/8 in: 79.8 fl oz, with 10 % extra 87.8 fl oz (6.75 lb); at 1 : 1 that is 43.9 fl oz resin and 43.9 fl oz hardener.
- Round tray 12 in, 1/4 in deep: 15.7 fl oz.
- 60 fl oz at 5 : 1 by volume: 50 fl oz resin + 10 fl oz hardener.
- Table 6 × 3 ft, 1/4 in, 10 % extra: 3.09 gal, about 30.4 lb.
For other shapes, find the volume with the volume calculator; the density calculator converts between weight and volume.
Tips and limits
Mix only what you can pour in time: the data sheet of WEST SYSTEM 105/205 gives a pot life of 9 to 12 minutes for 100 g at 72 °F – larger batches in a cup get hot faster. Many coating epoxies may only be poured in thin layers; deep pours need a casting resin made for it. The 10 % extra is a rule of thumb for drips, cup residue and edges. Wear gloves and work in a ventilated room.
Frequently asked questions
How much epoxy do I need for a table?
Length × width × thickness. A 48 × 24 in table at 1/8 in needs 79.8 fl oz, about 88 fl oz with 10 % extra.
How do I convert cubic inches to fluid ounces?
Divide by 1.805: one US fl oz is 1.805 in³ (29.57 ml), one cubic inch is 16.387 ml.
What is the difference between mixing by volume and by weight?
Resin and hardener have different densities. WEST SYSTEM 105/205 is 5 : 1 by volume but 5.19 : 1 by weight – always use the type your label states.
How much does epoxy weigh?
Volume × density. With a specific gravity of 1.18 (WEST SYSTEM 105/205 cured), one liter weighs 1.18 kg and one US gallon about 9.85 lb.
How much extra should I mix?
About 10 % is a common rule of thumb for edges, drips and what stays in the cup; porous wood can take more for the first coat.
Can I pour epoxy thicker than 1/4 inch?
Only if the product allows it. Coating epoxies are made for thin layers; for deep pours use a casting resin and follow its maximum depth.
Sources and legal basis
As of: · Editorial policy
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