Understanding masterbatch let-down ratio

The let-down ratio (LDR) tells you how much colour or additive masterbatch to blend into base resin. It is written like 1:25 or 4%, and the two forms mean the same thing — once you know the convention.

Two conventions

An LDR of 1:X can mean either "1 part masterbatch per X parts of the total blend" or "1 part masterbatch per X parts of base resin." They give slightly different addition percentages:

• Per total: addition % = 100 ÷ X. So 1:25 → 4.0%.
• Per base: addition % = 100 ÷ (X + 1). So 1:25 → 3.85%.

The gap is small at high dilutions but grows at rich loadings, so always confirm which your supplier means. MatQuo's let-down ratio calculator handles both and shows the masterbatch/base split explicitly.

From LDR to active additive

Addition % is only half the story: what usually matters is the active ingredient (pigment, slip, UV) reaching the polymer. If a masterbatch is 20% active and you add it at 5%, the active level is 1% (10,000 ppm). To hit a target ppm, work backwards with the active-additive calculator. For density-adjusted mass%↔volume% and multilayer film, use the masterbatch calculator suite. MatQuo does not publish recommended dosages — those come from your material supplier.