Masterbatch Dosage Guide: How to Calculate the Right Percentage

Too little masterbatch and colour looks washed out; too much and you're wasting money on every batch - here's how to get the ratio right.

By Siya Polymer & Speciality Chemicals Technical Team · Manufacturer & Supplier, Maharashtra, India

What Is Masterbatch Dosage?

Masterbatch dosage (also called letdown ratio) is the percentage of concentrated colour or additive masterbatch mixed into base resin to achieve the desired colour or effect. Getting this ratio right is the difference between consistent, cost-efficient colouring and batches that look inconsistent or cost more than necessary.

The Basic Formula

Dosage percentage is generally calculated as: (Masterbatch weight ÷ Total batch weight) × 100. For example, dosing 2 kg of masterbatch into 98 kg of base resin (100 kg total) gives a 2% letdown ratio - a common starting point for standard colour masterbatches.

Typical Dosage Ranges

• Colour masterbatch: typically 1-4% depending on pigment strength and target shade intensity
• White/opaque masterbatch: often higher, around 3-6%, since opacity requires more concentrate
• Black masterbatch: usually 1-3%, as carbon black has strong tinting power
• Functional additive masterbatch (UV, antioxidant, flame retardant): dosage is set by the required active-ingredient loading, not colour intensity, and can range widely - always follow the technical data sheet

Factors That Change the Right Dosage

• Base resin colour: a naturally translucent or off-white base needs less masterbatch than a naturally darker or opaque base
• Part wall thickness: thin-wall parts often need slightly higher dosage to achieve the same visual colour density as thick-wall parts
• Pigment strength: higher-quality, more concentrated masterbatches need lower dosage to hit the same shade
• Processing method: injection moulding, blow moulding and extrusion can each show colour slightly differently even at identical dosage

Common Dosage Mistakes

Under-dosing produces streaky, inconsistent colour and poor opacity, while over-dosing wastes material cost without meaningfully improving colour strength beyond a saturation point - and can sometimes affect mechanical properties or processing behaviour. The most reliable approach is to run a small trial batch at the supplier-recommended starting dosage, then fine-tune in small increments.

Getting a Recommendation

Because pigment strength and base resin interact, the ideal dosage genuinely varies batch to batch - sharing your base resin type, target Pantone/shade reference and part specification with a technical team gets you a far more accurate starting dosage than a generic percentage.