How do you calculate letdown ratio?

Divide the letdown vehicle weight by the mill-base or concentrate weight, then apply the conversion basis. With 1,800 lb vehicle, 600 lb mill base, and a basis of 1, the ratio is 3x.

What does a 3:1 letdown ratio mean?

It means 3 lb of letdown vehicle for every 1 lb of mill base, as in the example. The finished batch is three parts vehicle to one part concentrate by the chosen basis.

Why keep numerator and denominator on the same basis?

Mixing a per-batch vehicle weight with a per-gallon concentrate weight produces a meaningless ratio. Both weights must come from the same batch, formula, or unit basis for the 3x result to be valid.

What is the conversion basis for?

It scales the raw ratio to whatever convention you report in. A basis of 1 leaves the raw 3 unchanged; use it to convert to parts-per or other house conventions without redoing the division.

Letdown ratio vs pigment loading, what's the difference?

Letdown ratio is a weight relationship between vehicle and concentrate. Pigment loading is the actual pigment percentage in the finished product, which also depends on the concentrate's own pigment content, so equal ratios can still differ in loading.

Does a higher letdown ratio mean weaker color?

Generally yes, more vehicle per unit of mill base dilutes pigment, lowering color strength and usually viscosity, assuming the same concentrate.

Coatings, Inks & Specialty Chemical Production calculator

Letdown Ratio Calculator

Letdown ratio expresses how much letdown vehicle, the resin-and-solvent portion, is added per unit of mill base or pigment concentrate when finishing a coating or ink. It is the core dilution number that controls final pigment loading, color strength, and viscosity in a two-stage grind-and-letdown process. Formulators and batch operators use it to scale formulas, verify a batch ticket, and keep color strength consistent when substituting concentrates. Because mill base is the expensive, pigment-heavy component, a wrong letdown ratio shows up immediately as off-strength or off-viscosity product.

What this calculator does

Calculate letdown ratio from letdown vehicle weight, mill-base or concentrate weight, and any conversion basis.
scaling a formula or checking the balance between mill base and letdown vehicle
It divides letdown vehicle weight by mill-base or concentrate weight, applies a conversion basis, and returns the dilution ratio as an x value.

Formula used

Letdown Ratio = letdown vehicle weight ÷ mill-base or concentrate weight × ratio conversion basis
Keep the numerator and denominator on the same batch, formula, or production basis.

Inputs explained

Letdown vehicle weight:
Mill-base or concentrate weight:
Ratio conversion basis:

How to use the result

Use it when finishing a ground dispersion, scaling a formula up or down, or checking that a batch ticket's letdown matches the intended ratio.
It is a weight ratio only; it doesn't account for solids content or pigment loading differences between concentrates, so equal ratios can still yield different color strength.

Current U.S. benchmarks

Industrial electricity averages 8.66 cents per kWh across the U.S. (EIA, Apr 2026), up 5.5% from a year earlier. Energy-intensive steps carry this directly into unit cost.
The producer price index for industrial chemicals stands at 344.336 (BLS, May 2026), up 16.1% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 14,543 chemical manufacturing establishments employing about 911,245 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate letdown ratio? Divide the letdown vehicle weight by the mill-base or concentrate weight, then apply the conversion basis. With 1,800 lb vehicle, 600 lb mill base, and a basis of 1, the ratio is 3x.
What does a 3:1 letdown ratio mean? It means 3 lb of letdown vehicle for every 1 lb of mill base, as in the example. The finished batch is three parts vehicle to one part concentrate by the chosen basis.
Why keep numerator and denominator on the same basis? Mixing a per-batch vehicle weight with a per-gallon concentrate weight produces a meaningless ratio. Both weights must come from the same batch, formula, or unit basis for the 3x result to be valid.
What is the conversion basis for? It scales the raw ratio to whatever convention you report in. A basis of 1 leaves the raw 3 unchanged; use it to convert to parts-per or other house conventions without redoing the division.
Letdown ratio vs pigment loading, what's the difference? Letdown ratio is a weight relationship between vehicle and concentrate. Pigment loading is the actual pigment percentage in the finished product, which also depends on the concentrate's own pigment content, so equal ratios can still differ in loading.

Last reviewed 2026-05-12.