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mg/kg to PPM Converter
↔ Convert ppm to mg/kg instead

Common Conversions

mg/kg ppm
0.01 0.01
0.1 0.1
1 1
5 5
10 10
50 50
100 100
400 400
1000 1000
5000 5000
10000 10000

Why this conversion matters in chemistry

For solid samples — soil, sediment, food matrices, biota — mg/kg and ppm describe the same thing. Both are milligrams of analyte per kilogram of sample. The factor is exactly 1, but the conversion still earns its keep at the boundary between an analytical method and a regulatory report. A 150 mg/kg total petroleum hydrocarbons result on a soil sample is 150 ppm in EPA risk-assessment language. The identity holds rigorously for mass per mass; for liquid samples reported in mg/L, the equivalence depends on density being close to 1 g/mL.

Formula

ppm = mg/kg × 1 (mass/mass)

Worked Examples

1 mg/kg = 1 ppm

The identity itself — one milligram of analyte per kilogram of solid sample is one part per million by mass.

400 mg/kg = 400 ppm

The long-standing EPA residential soil screening level for lead, expressed in either notation.

0.5 mg/kg = 0.5 ppm

A sub-ppm contaminant — at the edge of routine ICP-MS sensitivity for many trace metals in solid matrices.

50 mg/kg = 50 ppm

A moderately elevated contamination level — well above background for most regulated compounds.

Frequently Asked Questions

Is mg/kg always the same as ppm?
For mass per mass concentrations, yes — both mean milligrams per kilogram, exactly. Where it can drift is when ppm is taken as mass per volume in a liquid sample, since liquid density enters the relationship.
How is mg/kg measured in the lab?
Digest or extract the solid sample, measure the analyte concentration in the extract by ICP-MS, AAS, or LC-MS, then calculate back to mg per kg of original solid using the mass digested and the volume of extract.
What's the difference between mg/kg and mg/L?
mg/kg is mass per mass — used for solids. mg/L is mass per volume — used for liquids. They become numerically equal when the liquid density is close to 1 g/mL, which is most aqueous samples but not concentrated brines or non-aqueous solvents.
What units do food-safety regulations use?
FDA and EU food contaminant limits are typically given in mg/kg, or µg/kg for ppb-scale limits. Both conventions reflect the mass per mass framing that mg/kg and ppm share for solid matrices.