Blending Ratio Calculator
Calculate the required ratio of two components to achieve a target property (e.g., concentration, viscosity index, octane number, proof) using the lever rule / mixing rule.
Property value of pure Component A (e.g., octane number, % concentration, viscosity)
Property value of pure Component B
Desired property value of the final blend (must be between A and B)
If provided, calculates absolute quantities of each component
Unit for the total volume/mass display
Formula — Lever Rule (Linear Mixing Rule)
For a two-component blend where the property mixes linearly:
Pblend = xA · PA + xB · PB
where xA + xB = 1
Solving for the fraction of Component A:
xA = (Ptarget − PB) / (PA − PB)
xB = 1 − xA
Absolute quantity of each component given total volume/mass V:
QA = xA · V QB = xB · V
Assumptions & References
- The property of interest mixes linearly by volume or mass fraction (ideal mixing / lever rule). This is valid for many concentration, proof, and index blending problems.
- Non-linear properties (e.g., viscosity blending, octane blending index) require property-specific blending indices and are not covered here.
- The target property value must lie strictly between (or equal to) the two component values; extrapolation is not physically meaningful for blending.
- The simplified integer ratio is computed via the Greatest Common Divisor (GCD) of the scaled fractions (scale = 10,000).
- Reference: ASTM D4177 (blending), API Technical Data Book — Petroleum Refining (linear blending rules).
- Reference: Perry's Chemical Engineers' Handbook — mixture property calculations.