Epoxy Mix Ratio Calculator
Hardener needed (grams)
50.0
How it works
Epoxy systems consist of two components — resin and hardener — that must be mixed in precise ratios by weight or volume. Incorrect ratios leave the epoxy partially uncured, resulting in a sticky, weak surface. The Epoxy Mix Ratio Calculator converts manufacturer ratios to actual volumes or weights for any batch size.
**Weight vs. volume ratio** Epoxy ratios are specified either by weight or by volume. These are not interchangeable — resin and hardener have different densities. A "2:1 by weight" system and a "2:1 by volume" system have different actual proportions. Always use the ratio type specified by the manufacturer.
**Mixing tolerance** Most epoxy systems tolerate plus/minus 5% ratio variation. Beyond that, excess resin leaves tacky spots; excess hardener produces brittle areas. Use a calibrated digital scale for critical applications.
**Pot life and cure time** Pot life ranges from 5 minutes (fast-cure) to several hours (slow-cure marine epoxies). Larger batches exotherm faster — heat accelerates cure. Pour large pours into wide, shallow molds rather than deep containers to extend working time.
**Bubbles and surface defects** Bubbles form when mixing too vigorously. A brief pass with a heat gun pops surface bubbles. Do not overheat: above 140 degrees F, epoxy can yellow or cure with a wavy surface. Thin pours under 1/4 inch are less prone to exotherm and bubbling.
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Frequently Asked Questions
- Sticky or soft epoxy after the specified cure time almost always indicates incorrect mix ratio. Excess resin (too little hardener) leaves the cure incomplete — the amine hardener isn't present in sufficient quantity to cross-link all the epoxy groups. Excess hardener leaves unreacted amine compounds on the surface — often visible as a white, oily 'amine blush.' Both produce sticky surfaces. Remedies: if still workable (under 4 hours), scrape off and re-pour with correct ratio. For cured-but-sticky epoxy: a thin, correctly-mixed coat of epoxy applied over the sticky surface can sometimes cure it by providing the missing reactive partner — test in an inconspicuous area first. In many cases, you must strip back to substrate and start over.
- Yellowing in clear epoxy has two causes: UV exposure and heat. UV light breaks down the aromatic chemical bonds in standard epoxy, causing yellowing within months of light exposure. Solution: use UV-stabilized (UV-resistant) epoxy formulations for light-exposed applications (tabletops, outdoor bar tops). UV-stable epoxy contains hindered amine light stabilizers (HALS) and UV absorbers that slow but don't completely prevent yellowing. For deep UV resistance, apply a UV-inhibiting topcoat (marine varnish, UV-blocking polyurethane) over cured epoxy. Heat yellowing: epoxy exotherming (getting very hot during cure) yellows irreversibly. Prevent by pouring in thin layers (under 1/2 inch for most casting resins) and using low-exotherm formulations for deep pours.
- Coating epoxy (table top resin) is formulated for thin pours — 1/8 to 1/4 inch maximum per layer. It has a shorter pot life and generates low heat over a larger surface area. It self-levels and is typically used for river tables, tabletops, art projects, and surface sealing. Casting epoxy is formulated for thick pours — 1/2 inch to 2 inches per layer, with ultra-low exotherm formulas allowing even deeper pours. It has longer pot life to allow working time in larger volumes. Using coating resin in thick pours generates excessive heat that can yellow, crack, or even catch fire. Always use the product specified for your application depth.
- Epoxy-compatible colorants: liquid epoxy pigments (purpose-made, guaranteed compatible), alcohol inks (most brands compatible, very vibrant, small amounts needed), mica powder pigments (metallic and pearlescent effects, very popular for river tables), acrylic paint (use sparingly — less than 10% of total volume or it weakens the epoxy). Incompatible colorants that inhibit cure: oil-based paints and stains, regular food coloring (water disrupts cure), candle dyes (often oil-based). Important: add colorant to the resin component first, mix thoroughly, then add hardener and mix to ratio. This ensures colorant is evenly distributed before the exotherm begins. Test small batches before committing to large pours.