How to Calculate Weighted Average Assay for DMA 40% Purchases
2026-11-12
China Amines Co., Limited
Customers reviewing dimethylamine 40% aqueous solution purchases with China Amines Co., Limited may want to summarize several batches in one monthly report.
When batch quantities differ, use a mass-weighted average to represent the purchased material’s calculated overall DMA content. Each batch contributes according to its net solution weight.
Start with comparable batch records
Collect the net solution quantity and accepted assay for each batch.
Confirm that every assay uses the same concentration basis. Manufacturer specifications identify DMA 40% as an aqueous grade with defined assay requirements and test methods.
Keep the supplier batch number and supporting COA linked to each entry.
Calculate contained DMA first
For each batch:
Contained DMA = Net solution mass × DMA mass fraction
Consider these hypothetical purchasing records:
| Batch | Net solution weight | Assay, w/w | Calculated contained DMA |
|---|---|---|---|
| A | 5,000 kg | 39.8% | 1,990 kg |
| B | 10,000 kg | 40.2% | 4,020 kg |
| Total | 15,000 kg | — | 6,010 kg |
The figures illustrate the calculation and do not establish acceptance limits.
Divide total DMA by total solution weight
Calculate the weighted average:
Weighted average assay (%) = Total contained DMA ÷ Total solution mass × 100
For the example:
6,010 ÷ 15,000 × 100 ≈ 40.07%
A simple average of the two assay values would give 40.0%. The weighted result reflects Batch B’s larger contribution to the purchased quantity.
Define what the report covers
Identify whether the calculation summarizes receipts during a period or stock remaining at a particular date.
For a remaining-stock report, use each batch’s remaining net quantity. Preserve individual inspection and release status alongside the summary.
This calculation describes an accounting summary of the selected records. Establish the composition of material in shared storage through the site’s approved inventory and analytical procedures.
Keep the calculation traceable
Retain the original quantities, assay values, units, and calculation formula. Round the final result appropriately for the input data.
For DMA 40% inquiries, send China Amines Co., Limited your required quantity basis, approved specification, packaging preference, destination, and batch-documentation requirements.
Inquiries: info@chinaamines.com