Compliance & ContractsFree calculatorPDF, Excel, Word exportElectronics Manufacturing

RoHS Homogeneous Material Limit Margin Calculator

RoHS compliance is decided at the level of the homogeneous material, which is a material of uniform composition that cannot be separated mechanically. This calculator turns mass data into the weight percent that you compare with the maximum concentration value.

Your numbers

Restricted substance mass

Mass of the restricted substance (for example lead) measured or declared in the homogeneous material.

Homogeneous material mass

Mass of the single homogeneous material that holds the substance, such as one solder joint or one plastic housing.

Maximum concentration value

Measurement uncertainty

10 %

Relative uncertainty of your XRF or ICP result. Used to flag results that are close to the limit.

Your results

Concentration in homogeneous material

0.05

Weight percent of the substance in the homogeneous material.

Within limit after uncertainty (1 = yes)

Applies your measurement uncertainty on the high side before comparing with the limit.

Utilisation of the limit

50%

100% means you are exactly at the maximum concentration value.

Margin to limit

0.05

Weight percent points remaining before the limit. Negative means over the limit.

Maximum allowed substance mass

1.2

Largest mass of the substance that keeps this material within the limit, in mg.

Within limit (1 = yes, 0 = no)

RoHS limits apply to each homogeneous material, not to the whole product. Exemptions in Annex III and IV of Directive 2011/65/EU can change the outcome. This is a screening calculation, not a declaration of conformity.

Save results:

Concentration vs substance mass

Sweeps Restricted substance mass from 0 to 3, holding your other inputs fixed.

Automate substance screening from your ERP

Optional expert review of how to connect RoHS and material declarations to your item master.

Optional. The tool and every export work without this. No spam.

How to use the calculator

Enter the mass of the restricted substance and the mass of the homogeneous material that contains it, then choose the limit. Cadmium has a limit of 0.01% by weight; lead, mercury, hexavalent chromium, PBB, PBDE and the four listed phthalates share 0.1%. Set the measurement uncertainty of your analytical method so the tool also checks the result on the high side. The chart sweeps substance mass so you can see where the result crosses the limit.

Use the mass of the material, not of the whole component
Pick 0.01% only for cadmium
Enter uncertainty from your lab report if you have it
Re-run for every homogeneous material in the part

The method behind the numbers

Concentration is substance mass divided by homogeneous material mass, multiplied by 100. The result is compared with the maximum concentration value in Annex II of the RoHS recast directive. A part passes only if every homogeneous material passes, so a small solder joint with a high lead share can fail a part whose total lead content looks tiny. The uncertainty check multiplies the result by one plus the relative uncertainty, which is a conservative way to decide whether a borderline result should be accepted.

Concentration = substance / material x 100
Utilisation = concentration / limit
Max mass = limit x material mass

Worked example and how to read the result

A 1,200 mg plastic housing is found to contain 0.6 mg of a restricted substance. That is 0.05%, which is 50% of the 0.1% limit and leaves 0.05 points of margin. With 10% uncertainty the high-side value is 0.055%, still inside the limit. If the same mass were found in a 400 mg material the result would be 0.15% and would fail. Treat anything above about 80% utilisation as a signal to ask for more evidence from the supplier.

Below 50% utilisation: normally comfortable
80% to 100%: ask for a test report
Above 100%: check for an exemption or replace the material

Common mistakes

The most common error is dividing by the mass of the whole product or the whole component, which hides a failing material. Another is applying 0.1% to cadmium. Teams also forget that an exemption is specific to an application and has an expiry date, so a part that relies on one needs the exemption number recorded in the material declaration. In an ERP the result should live on the item or the supplier declaration record, not in a spreadsheet nobody can find at audit time.

Frequently Asked Questions

What is a homogeneous material under RoHS?

It is a material of uniform composition throughout, or a material made of a combination of materials that cannot be disjoined or separated into different materials by mechanical actions such as unscrewing, cutting, crushing, grinding or abrasive processes. A plated layer counts separately from its substrate.

Why is cadmium limited to 0.01%?

The directive sets the maximum concentration value for cadmium at 0.01% by weight in homogeneous materials, ten times stricter than the 0.1% that applies to lead, mercury, hexavalent chromium, PBB, PBDE and the listed phthalates.

Can I average the substance over the whole component?

No. The limit applies per homogeneous material. Averaging across a component dilutes the concentration and can hide a material that exceeds the limit, which is the main reason this method is rejected in audits.

Does passing this calculator mean my product is RoHS compliant?

No. It is a screening check for one material and one substance. Compliance also needs technical documentation, exemption handling, a declaration of conformity and the CE marking process that applies to your product.

If your RoHS evidence is scattered across supplier PDFs and spreadsheets, Netray can help you pull it together against your ERP item master and flag items with no current declaration.

Talk to an Expert Explore More Free Tools

Related Tools

Compliance & Contracts

More Compliance & Contracts tools

See all

Back to All Tools