Paint Mixing Ratio Calculator
Mixing two-part or three-part paints, epoxies, and coatings to the correct ratio is critical for the coating to cure properly and adhere well. Too much hardener or too little resin will produce a coating that is brittle, soft, or fails entirely. The mixing ratio is always specified in the product data sheet as a volume or weight ratio such as 4:1, 2:1:1, or 1:1. This calculator takes any 2-component or 3-component ratio, your desired total volume, and your preferred unit of measurement, then outputs the exact amount of each component you need to measure out. Results are shown simultaneously in fluid ounces, millilitres, cups, and gallons so you can use whichever measuring tool you have on hand. You can also label each component (Part A, Part B, etc.) with custom names for clarity. The reference table at the bottom lists common paint and coating systems with their standard ratios.
Ratio -- at -- total
Part A
Part B
Part C
Mixing ratio formulas
total_volume_ml = convert(total_volume, selected_unit, ml)
ml_per_part = total_volume_ml / total_parts
volume_A_ml = ratio_A * ml_per_part
volume_B_ml = ratio_B * ml_per_part
volume_C_ml = ratio_C * ml_per_part (if applicable)
Unit conversions:
1 fl oz = 29.5735 ml
1 cup = 8 fl oz = 236.588 ml
1 gallon = 128 fl oz = 3,785.41 ml
1 litre = 1,000 ml
Common paint and coating ratios reference
| Product type | Typical ratio | Notes |
|---|---|---|
| Two-part epoxy resin (craft) | 1:1 | By volume; check product label |
| Automotive urethane clear coat | 4:1 | Base to hardener by volume |
| Two-part polyurethane topcoat | 3:1 or 4:1 | Varies by manufacturer |
| Automotive basecoat with reducer | 1:1 | By volume; some products 2:1 |
| Two-part epoxy primer | 4:1 | Base to activator by volume |
| Clear coat with hardener and reducer | 4:1:1 | 3-component system |
| Marine epoxy | 5:1 | Resin to hardener by volume |
Always verify the ratio against the product data sheet (PDS) for the specific brand and product you are using. Ratios are not interchangeable between different brands or systems.
Paint mixing ratio calculator: frequently asked questions
What is a paint mixing ratio?
A paint mixing ratio tells you how much of each component to combine. For example, a 2:1 ratio of base coat to hardener means for every 2 parts of base, you add 1 part of hardener, giving 3 parts total. Ratios can be by volume (most common for paint) or by weight. This calculator uses volume ratios. Always check the product data sheet for your specific paint or coating system to confirm the correct ratio.
What is the difference between a 2-component and 3-component ratio?
A 2-component (2K) paint system mixes two materials: typically a base coat or resin, and a hardener or catalyst. Examples include two-part epoxy, polyurethane topcoats, and automotive clear coats. A 3-component system adds a third element, usually a thinner or reducer, at a specified ratio. This calculator handles both 2K and 3K mixing ratios.
How do I convert fl oz to ml?
1 US fluid ounce = 29.5735 ml. The calculator shows results in all major units simultaneously: fluid ounces, millilitres, cups (1 cup = 8 fl oz), and gallons (1 gallon = 128 fl oz). All conversions use these standard US unit definitions.
Why does the ratio matter for paint quality?
Two-part paints and coatings cure through a chemical reaction between the base and hardener. Using the wrong ratio upsets the chemistry: too much hardener can cause brittleness or poor adhesion; too little hardener leaves the coating soft, uncured, or prone to peeling. Always use the manufacturer-specified ratio. Ratios are not interchangeable between different paint systems.
What are common paint mixing ratios?
Common ratios vary by product type. Automotive basecoats with reducer: often 1:1 or 2:1. Two-part urethane clear coats: typically 4:1 or 2:1 (base to hardener). Two-part epoxy primers: commonly 4:1. Two-part epoxy resins for crafts: often 1:1. Automotive touch-up with thinner may use 3-component ratios like 4:1:1 (base, hardener, reducer). Always verify the specific product data sheet.
Sources and methodology
- Unit conversion factors: US customary volume standards (1 fl oz = 29.5735 ml; 1 cup = 8 fl oz; 1 gallon = 128 fl oz).
- Common ratio reference values are typical industry examples only. For any specific product, always use the manufacturer-supplied product data sheet.
- EPA guidance on architectural and industrial coatings: US EPA: AIM Coatings.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. This calculator performs volume ratio calculations only. Always consult the product data sheet for the correct ratio for your specific coating system. See our methodology.