MEKP Calculator for Polyester Resin
Find how much MEKP catalyst to add to polyester or fiberglass resin. Enter the amount of resin and the percent from your label to get ml and approximate drops.
Add MEKP
– ml
about – drops
| Resin | – |
| MEKP (cc) | – |
| MEKP (g, approx.) | – |
Next steps
Convert ounces, ml and gramsMixing epoxy instead? Use the ratio calculatorSafety first
- MEKP is a strong chemical. Wear safety glasses and nitrile gloves, and work with good ventilation.
- Never mix MEKP directly with cobalt or other accelerators; it can react violently. Add it only to resin.
- This calculator does the math only. Always follow the catalyst range and instructions on your resin's label.
How to use this calculator
- Enter the amount of polyester or fiberglass resin you will mix.
- Enter the MEKP percent from the label (often 1–2% at room temperature).
- Measure the MEKP with a small syringe or a dropper bottle, then stir it in completely.
How the calculation works
- MEKP (ml) = resin (ml) × percent ÷ 100
- 1 fl oz = 29.57 ml; 1 ml = 1 cc
- Drops = ml × drops per ml (about 20 for many bottles)
MEKP chart
Milliliters of MEKP (approximate drops at 20 per ml):
| Resin | 1% | 1.5% | 2% |
|---|---|---|---|
| 1 fl oz | 0.3 ml (6 drops) | 0.44 ml (9 drops) | 0.59 ml (12 drops) |
| 4 fl oz | 1.2 ml (24 drops) | 1.8 ml (35 drops) | 2.4 ml (47 drops) |
| 8 fl oz | 2.4 ml (47 drops) | 3.5 ml (71 drops) | 4.7 ml (95 drops) |
| 16 fl oz (1 pint) | 4.7 ml (95 drops) | 7.1 ml | 9.5 ml |
| 1 quart | 9.5 ml | 14.2 ml | 18.9 ml |
| 1 gallon | 37.9 ml | 56.8 ml | 75.7 ml |
Frequently asked questions
How much MEKP do I add to polyester resin?
Most polyester and fiberglass resins use about 1% to 2% MEKP at room temperature. For 1 fl oz of resin at 1%, that is about 0.3 ml, or roughly 6 drops. Always use the amount on your resin's label.
How many drops of MEKP per ounce of resin?
At about 20 drops per ml, 1% is about 6 drops per fluid ounce and 2% is about 12 drops. Drop size changes with the bottle, so a small syringe marked in ml is more accurate.
Should I use more MEKP when it is cold?
Resin labels often allow a little more catalyst in a cool room and less in a hot room or for thick castings, but stay inside the range the manufacturer gives. Too much MEKP can make the resin crack, yellow or get very hot.
Can I use MEKP with epoxy resin?
No. MEKP is a catalyst for polyester and vinyl ester resins only. Epoxy cures with its own hardener, mixed at the ratio on the label.