Home & DIY
How much epoxy resin do you need for a pour?
Grams of resin and hardener for your mold or river table from its dimensions and the mixing ratio.
Quick answer
Epoxy is unforgiving arithmetic: mold volume in ml × density (~1.1 g/ml), split between components A and B exactly as the label commands. Example: 500 ml mold volume at ratio 2:1 by weight → about 550 g total mix (367 g resin + 183 g hardener), plus a 5% margin for cup walls and stir sticks. Get the ratio wrong by eye and the pour stays tacky forever — there is no fixing a bad mix, only chiseling it out.
Total mix to prepare
~2,772 g
- Component A (resin)
- 1,848 g
- Component B (hardener)
- 924 g
- Mold volume
- 2.4 L (0.6 US gal)
Weights use epoxy’s density of ~1.1 g/ml plus a 5% margin for what stays on cup walls and stir sticks. The ratio must come from your kit’s label and be respected by weight on a scale — "roughly" is how pours stay sticky forever. Check your resin’s maximum pour depth too: casting resins accept 2-5 cm per layer, coating resins only millimeters; deeper pours overheat, yellow and crack. For river tables, pour in layers and wait for each to gel.
How it works
Casting vs coating vs floor: casting resin allows 2–5 cm per pour (rivers, molds, jewelry) — go deeper only in layers after gel. Coating / tabletop resin is 1–3 mm and self-levels. Floor epoxy on concrete is usually 1–3 mm total film (primer + coats) — coverage often 0.8–1.5 kg/m² depending on system; measure area × thickness × density, not mold volume. Exceed max pour depth and the exotherm runs away (yellowing, bubbles, cracks).
Use a scale: most kit ratios are by weight. A €10 digital scale with 0.1 g resolution beats volume measuring. Mix slowly, scrape cup walls, warm bottles if the shop is cold, pop bubbles with a heat gun. For poured epoxy floors, substrate prep often needs a concrete grinder buy or rent — diamond discs are the recurring buy.
Mass and depth matter as much as the ratio, because the reaction makes its own heat. A thick pour or a large batch left sitting in the mixing cup gets hot enough to yellow, crack or in extreme cases smoke — which is the real reason casting resins state a maximum depth per layer rather than a maximum volume. Two habits keep it under control: pour deep work in stages, letting each layer gel first, and mix in a wide shallow container rather than a tall narrow one, so the heat has somewhere to go. And never leave mixed resin standing in the cup while you set up.
Highlighted links go to Amazon.
Frequently asked questions
How much resin for a river table?+
Measure the river channel as a box — length × average width × slab thickness — and expect big numbers: a 180 cm table with a 12 cm river and 4 cm slab is ~8.6 liters, roughly 9.5 kg of mix, poured in two or three layers. At typical casting-resin prices that’s €150-300 of material, which is why measuring twice matters. Seal the wood edges with a thin epoxy coat first, or the wood drinks resin and burps bubbles into the river for hours.
How much epoxy per m² for a floor?+
Many floor systems land around 0.8–1.5 kg/m² total for primer plus wearing coats — check your TDS. A 20 m² garage at 1.2 kg/m² needs about 24 kg of mixed epoxy before waste. Do not use deep-pour casting resin as a thick floor slab.
What’s the difference between casting and coating resin?+
Chemistry tuned for opposite jobs. Casting resin cures slowly (24-72 h) and cool, allowing 2-5 cm pours — it’s what rivers, molds and jewelry blocks want. Coating resin cures fast and hot in thin layers (1-3 mm), self-levels and resists yellowing — it’s for tabletop finishes and art surfaces. Pour coating resin deep and it boils; cast in thin coats and you wait days per millimeter. Check the label’s max pour depth before buying, not after.
Why did my resin stay sticky?+
Three culprits in order of frequency: ratio error (measured by volume when the label says weight, or eyeballed), insufficient mixing (3+ minutes, scraping walls and bottom — the film on the cup wall is unmixed and ends up somewhere), and cold (below ~18 °C curing slows drastically or stalls). A surface that’s tacky but hard underneath can sometimes be rescued with a fresh correctly-mixed coat; a soft gooey mass cannot — chisel, clean with alcohol, start over.
As an Amazon Associate I earn from qualifying purchases — the price does not change for you.