Calculate the total cost of a laboratory peptide purchase

Use a cost boundary you can explain

For a purchasing comparison, our suggested budget is material subtotal plus shipping, applicable nonrecoverable taxes or import charges, payment fees, and additional verification costs. Include internal handling costs only if your team has a defensible estimate and applies it consistently. Record recoverable taxes separately with your finance team's guidance.

These are budgeting categories, not a statement that any particular tax or fee applies. Use the actual destination, written quotation, and your institution's purchasing rules. Leave unknown charges visibly unresolved instead of entering zero.

A worked example with invented numbers

The following USD figures are hypothetical arithmetic only, not supplier prices or current market estimates. Assume each quotation covers the same documented quantity basis and meets the same laboratory acceptance requirements.

• Quote A: 100 + 20 + 8 + 60 = 188.
• Quote B: 120 + 10 + 0 + 30 = 160.
• Quote B costs $28 less under these assumptions, despite its higher material subtotal.
• If Quote B instead needs $60 of verification, its total becomes $190 and the comparison changes.

Do not compare unlike quantities

Merck distinguishes gross weight from net peptide content and notes that purity is a different attribute. Carry the supplier's quantity definition into your spreadsheet. Two labels with the same nominal mass are not a sufficient basis for a normalized comparison if the quoted definitions differ.

Our suggested formula is total documented purchasing cost divided by the accepted quantity on a common, documented basis. If the basis cannot be reconciled, compare order totals with a visible limitation and ask for clarification. Do not estimate a usable research yield from an HPLC percentage alone. This guide provides no dosing, preparation, administration, or human-use calculation.

Make uncertainty visible before approval

Save one base case using confirmed charges and one sensitivity case using clearly labeled assumptions. Examples include another shipping charge or a separate analytical quotation. Do not assign a supplier failure probability without data; use a scenario instead.

Finish the purchase note with the quotation date, expiry, currency, quantity basis, missing costs, and person responsible for resolving them. A cheaper total is useful only after the documentation requirement has been met. Our downloadable checklist includes cost rows so the evidence and budget can travel together without creating an account or sending us data.