# RoHS Homogeneous Material Limit Margin Calculator > Source: https://netray.co/tools/rohs-homogeneous-material-limit-margin-calculator > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Convert lab or supplier mass data into a weight percent per homogeneous material and see how much margin you have to the RoHS maximum concentration value. ## Category compliance-legal ## Industry Electronics Manufacturing ## Audience - Compliance engineer - Supplier quality - Materials engineer ## Tool **Kind:** calculator **Inputs:** #### Restricted substance mass **Key:** substance_mg **Type:** number **Default:** 0.6 **Min:** 0 **Step:** 0.1 **Unit:** mg **Help:** Mass of the restricted substance (for example lead) measured or declared in the homogeneous material. #### Homogeneous material mass **Key:** material_mg **Type:** number **Default:** 1200 **Min:** 0.001 **Step:** 10 **Unit:** mg **Help:** Mass of the single homogeneous material that holds the substance, such as one solder joint or one plastic housing. #### Maximum concentration value **Key:** limit **Type:** select **Default:** 0.1 **Options:** ##### 0.1% (Pb, Hg, Cr6+, PBB, PBDE, four phthalates) **Value:** 0.1 ##### 0.01% (Cd) **Value:** 0.01 #### Measurement uncertainty **Key:** uncertainty **Type:** slider **Default:** 10 **Min:** 0 **Max:** 40 **Step:** 1 **Unit:** % **Help:** Relative uncertainty of your XRF or ICP result. Used to flag results that are close to the limit. **Outputs:** #### Concentration in homogeneous material **Key:** pct **Expr:** substance_mg / material_mg * 100 **Format:** decimal **Primary:** true **Description:** Weight percent of the substance in the homogeneous material. #### Utilisation of the limit **Key:** util **Expr:** pct / limit * 100 **Format:** percent **Description:** 100% means you are exactly at the maximum concentration value. #### Margin to limit **Key:** margin **Expr:** limit - pct **Format:** decimal **Description:** Weight percent points remaining before the limit. Negative means over the limit. #### Maximum allowed substance mass **Key:** max_mg **Expr:** limit / 100 * material_mg **Format:** decimal **Description:** Largest mass of the substance that keeps this material within the limit, in mg. #### Within limit (1 = yes, 0 = no) **Key:** pass_flag **Expr:** lte(pct, limit) **Format:** integer #### Within limit after uncertainty (1 = yes) **Key:** safe_flag **Expr:** lte(pct * (1 + uncertainty / 100), limit) **Format:** integer **Primary:** true **Description:** Applies your measurement uncertainty on the high side before comparing with the limit. **Chart:** #### Concentration vs substance mass **Type:** line **X:** substance_mg **From:** 0 **To:** 3 **Steps:** 30 **Series:** - pct **Disclaimer:** 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. ## Content **Intro:** 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. **Sections:** #### How to use the calculator **Body:** 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. **Bullets:** - 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 **Body:** 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. **Bullets:** - Concentration = substance / material x 100 - Utilisation = concentration / limit - Max mass = limit x material mass #### Worked example and how to read the result **Body:** 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. **Bullets:** - 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 **Body:** 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. **Cta:** 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. **Faq:** #### What is a homogeneous material under RoHS? **Answer:** 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%? **Answer:** 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? **Answer:** 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? **Answer:** 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. ## Search terms rohs calculator, rohs homogeneous material calculation, rohs 0.1 percent limit calculator, rohs cadmium 0.01 percent, rohs threshold calculation, rohs compliance margin, maximum concentration value rohs, homogeneous material weight percent --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json