Convert mg/kg to percent by mass, or reverse the conversion. Equivalent ppm, ppb and g/kg values use the same total-sample mass basis.
mg/kg to Percent Formula
For a total-sample mass fraction, divide mg/kg by 10,000 to get percent by mass. Multiply percent by 10,000 to get mg/kg. The physical range is 0–1,000,000 mg/kg (0–100%). A medication amount per kilogram of body weight is a different ratio and cannot be interpreted as this sample concentration.
Variables:
- P is the percent concentration (%)
- mg/kg is the mass concentration in milligrams per kilogram of total sample (numerically equal to ppm by mass)
Key equivalence: 1 mg/kg = 1 ppm = 0.0001%. At 10,000 mg/kg, the concentration equals exactly 1%. This relationship holds for mass-based measurements in soils, foods, and solid materials.
| mg/kg (ppm) | Percent (%) |
|---|---|
| 0.1 | 0.000010 |
| 1 | 0.000100 |
| 5 | 0.000500 |
| 10 | 0.001000 |
| 25 | 0.002500 |
| 50 | 0.005000 |
| 75 | 0.007500 |
| 100 | 0.010000 |
| 150 | 0.015000 |
| 200 | 0.020000 |
| 250 | 0.025000 |
| 300 | 0.030000 |
| 400 | 0.040000 |
| 500 | 0.050000 |
| 750 | 0.075000 |
| 1000 | 0.100000 |
| 1500 | 0.150000 |
| 2000 | 0.200000 |
| 5000 | 0.500000 |
| 10000 | 1.000000 |
| * Rounded to 6 decimals. Conversion: Percent (%) = (mg/kg) / 10,000. | |
Real-World Concentration References
The examples below show the same mass-based values in mg/kg and percent. Regulatory reference points have specific scopes and dates, and natural concentrations vary. These conversions do not establish a safe concentration or determine compliance.
| Context | mg/kg (ppm) | Percent (%) | Source |
|---|---|---|---|
| EPA residential soil lead regional screening level (October 2025 CERCLA/RCRA directive) | 200 | 0.0200% | US EPA |
| EPA residential soil lead regional removal-management level (same directive) | 600 | 0.0600% | US EPA |
| EU general default pesticide MRL (exceptions apply) | 0.01 | 0.000001% | European Commission |
| Codex cadmium maximum level for wheat, whole commodity | 0.2 | 0.000020% | Codex CXS 193-1995 |
| USGS soil arsenic median, top 0–5 cm (conterminous US) | 5.2 | 0.00052% | USGS, SIR 2017-5118 |
| Approximate average ocean salinity by mass | 35,000 | 3.5% | NOAA |
| Estimated iron in Earth’s upper continental crust | 39,200 | 3.92% | USGS (citing Rudnick and Gao, 2003) |
| * EPA rows refer to the October 2025 CERCLA/RCRA directive; screening and removal-management levels serve different purposes and are not universal cleanup standards. The EU default has exceptions. Codex wheat covers common wheat, durum wheat, spelt and emmer. Verify current substance, commodity, matrix and jurisdiction requirements with the relevant authority. | |||
How to Calculate Percent from mg/kg
- Obtain the mg/kg value directly, or divide total milligrams by total kilograms to compute it.
- Divide the mg/kg value by 10,000 to convert to percent.
- To reverse the conversion (percent to mg/kg), multiply the percent value by 10,000.
Example:
A soil report gives 450 mg/kg lead. As a unit-conversion illustration, compare it with the 200 mg/kg residential regional screening level in EPA’s October 2025 CERCLA/RCRA directive:
Measured: 450 mg/kg / 10,000 = 0.045%
EPA residential screening reference: 200 mg/kg / 10,000 = 0.020%
The arithmetic difference is 250 mg/kg (0.025 percentage points). A screening level is not a cleanup standard or a universal safe/unsafe threshold; site-specific assessment and the applicable authority determine next steps.
