Last updated: July 3, 2026
Mixing Ratio Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The mixing ratio calculator computes r = mass_A / mass_B for two components, then reports the equivalent grams per kilogram as 1000r and a parts-style A:B ratio. For example, 5 g of A per 1000 g of B gives r = 0.005 and 5 g/kg.
The mixing ratio is the mass of component A divided by the mass of component B. Five grams divided by one thousand grams gives a mixing ratio of zero point zero zero five, or five grams per kilogram.
Key Takeaways
- Mixing ratio r equals mass of component A divided by mass of component B.
- Both masses must use the same unit so the ratio is dimensionless.
- The g/kg equivalent is r multiplied by 1000.
- Mixing ratio is not the same as mass percent because the denominator is not total mass.
- A ratio above 1 is valid when component A is more massive than component B.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
r = mass_A / mass_B; grams per kg = r × 1000
Where:
- r=Mixing ratio of component A to component B(kg/kg or g/g)
- m_A=Mass of component A(g)
- m_B=Mass of component B or reference material(g)
- 1000r=Equivalent grams of A per kilogram of B(g/kg)
Worked Examples
Humidity-style ratio: 5 g per 1000 g
Water vapor mass compared with dry-air mass gives a small mass mixing ratio.
- 1Write the ratio: r = mass_A ÷ mass_B.
- 2Substitute values: r = 5 g ÷ 1000 g = 0.005.
- 3Convert to grams per kilogram: 0.005 × 1000 = 5 g/kg.
Two-component mixture: 20 g per 80 g
Component A is one quarter of the mass of component B.
- 1Use r = mass_A ÷ mass_B.
- 2Substitute values: r = 20 g ÷ 80 g = 0.25.
- 3The equivalent value is 0.25 × 1000 = 250 g/kg.
Parts ratio: 3 g per 2 g
A component A mass larger than component B gives a mixing ratio above one.
- 1Use r = mass_A ÷ mass_B.
- 2Substitute values: r = 3 g ÷ 2 g = 1.5.
- 3This can be read as 3:2 parts or 1500 g/kg.
Introduction
A mixing ratio compares the mass of one component with the mass of another reference component: r = mass_A / mass_B. In atmospheric chemistry this is often the mass of water vapor per mass of dry air, reported as kg/kg or g/kg; in formulation work it can describe additive-to-carrier or component-to-component proportions. This calculator complements the mass percent calculator, which divides by total mixture mass, and the concentration calculator, which handles mass per volume. The unit treatment follows SI mass principles described by BIPM and IUPAC quantity terminology.
What is a mixing ratio?
A mass mixing ratio is the mass of component A divided by the mass of component B. The denominator is not the total mixture unless component B has been defined that way; it is the chosen reference component. Because both quantities are masses, r is dimensionless, but chemists and meteorologists often label it as kg/kg, g/g, or g/kg to make the convention clear.
r = 0.005 means 0.005 kg of A per 1 kg of B.
Multiplying by 1000 converts kg/kg or g/g to g/kg.
A parts expression A:B preserves the same mass proportion.
For percent by total solution mass, use the mass percent calculator.
Mixing ratio formula explained
The working equation is r = m_A / m_B. If m_A and m_B are entered in the same mass unit, the unit cancels. The calculator also reports grams per kilogram using 1000r, which is convenient for humidity and trace component reporting.
Do not add m_A and m_B in the denominator unless you want a mass fraction or mass percent instead of a mixing ratio.
How to calculate mixing ratio step by step
Measure the mass of component A and the mass of component B using the same unit. Divide A by B to obtain r. For g/kg, multiply r by 1000. To state the result as parts, keep the two masses in the form A:B or simplify the pair if exact integer parts are appropriate.
Record component A mass.
Record component B or reference mass.
Compute r = A ÷ B.
Compute g/kg = r × 1000.
Check that the denominator matches the scientific convention you intend to use.
Mixing ratio vs. mass fraction and mass percent
Mixing ratio compares A with B, while mass fraction compares A with the total mass A + B + other components. For 20 g A and 80 g B, the mixing ratio is 20/80 = 0.25, but the mass fraction is 20/100 = 0.20 and the mass percent is 20%. This difference is important in solutions, aerosols, humidity calculations, and recipes.
| Quantity | Formula | Example: 20 g A + 80 g B |
|---|---|---|
| Mixing ratio | m_A / m_B | 0.25 A/B |
| g/kg ratio | 1000 × m_A / m_B | 250 g/kg |
| Mass fraction | m_A / (m_A + m_B) | 0.20 |
| Mass percent | mass fraction × 100 | 20% |
Humidity and chemistry uses
Meteorology uses a water-vapor mixing ratio to compare water vapor mass with dry-air mass, a definition discussed in teaching resources from NOAA and atmospheric science texts. Chemistry and engineering use the same ratio structure for carrier gases, adsorbents, blends, brines, and reagent recipes where a component is specified relative to a reference material rather than the final total.
When reporting humidity-style values, specify whether you mean mixing ratio, specific humidity, or relative humidity; they are different quantities.
Accuracy tips and common mistakes
Most errors come from choosing the wrong denominator. If a label says g/kg dry air, the denominator is dry air only. If a formulation says parts A to parts B, the denominator is component B only. Make sure both masses use the same unit before dividing, and keep enough significant figures for small ratios such as 0.005.
Use the same mass unit for A and B.
Keep the denominator as component B, not total mass, for r.
Report g/kg for small ratios to avoid many leading zeros.
Use the dilution factor calculator for serial dilution workflows.
Quick Reference Card
Mixing Ratio — Quick Reference
Quick reference • Mixing Ratio Calculator
r = m_A / m_B; g/kg = 1000rValid range: 0 and above; values greater than 1 are valid when A has more mass than B
Common Values
⚠ Watch Out
- •Do not use total mixture mass unless calculating mass fraction.
- •Use the same mass unit for both inputs before dividing.
- •For humidity, use dry-air mass for the common mass mixing ratio convention.
- •Very small ratios may need scientific notation or g/kg for clear reporting.
- •Parts A:B is not the same as percent of total unless converted.
Pro Tips
- →Multiply r by 1000 to report grams per kilogram.
- →Scale batches by multiplying both A and B masses by the same factor.
- →Simplify integer parts ratios for recipes, but keep measured values for traceability.
- →Compare with mass percent when the final total mixture proportion matters.
- →State the denominator explicitly in reports, such as g water vapor per kg dry air.
FAQs
What does a mixing ratio of 0.005 mean?
It means the mass of component A is 0.005 times the mass of component B. Equivalently, there are 5 grams of A per kilogram of B.
Is mixing ratio the same as mass percent?
No. Mixing ratio divides by the mass of the reference component B, while mass percent divides by total mixture mass and multiplies by 100.
Can a mixing ratio be greater than 1?
Yes. If component A has more mass than component B, r is greater than 1. For example, 3 g A and 2 g B gives r = 1.5.
Why is g/kg reported as r times 1000?
Because 1 kilogram is 1000 grams. A dimensionless mass ratio of 0.005 corresponds to 0.005 kg per kg, or 5 g per kg.
What denominator should I use for humidity mixing ratio?
For the common meteorological mass mixing ratio, use the mass of water vapor divided by the mass of dry air, not the total moist-air mass.
How do I write a mixing ratio as parts A:B?
Use the two component masses as A:B. For 20 g A and 80 g B, the parts ratio is 20:80, which simplifies to 1:4.