A custom peptide has no list price because it has no fixed cost until the sequence, purity, fill and quantity are known. This guide walks through the inputs in the order a factory weighs them, explains what each one does to the number, and shows what a written quote from Pepti contains so you can read one from any supplier.
A catalogue peptide can have a list price because the factory has already paid for the synthesis, purified a lot, measured it and put it on a shelf. The remaining cost of your order is the fill, the label and the paperwork, which are predictable. A custom sequence is different: the synthesis has not happened yet, and its cost depends on how long the sequence is, how hard it is to build, how pure it must be, how much of it you need and how it must be presented. Until those are written down, a price is a guess, and a guess printed as a list price becomes a commitment the factory cannot keep.
So the honest answer to "what does a custom peptide cost" is a specification followed by a quote. That is not evasion; it is the only way the number can be right. This guide explains what the quote is made of so that the specification you send produces the quote you expect, and so that the number, when it arrives, makes sense.
One figure worth fixing early: on this desk a custom sequence starts at 100 kits, which is 1,000 vials, and a custom lot typically takes 15 days after the specification is confirmed and payment is received. The MOQ guide explains the first; the second is covered below under lead time.
Every custom quote is built from six inputs. They are also the six fields of a quotable specification, which is no coincidence: the specification exists to feed the quote.
| Input | What it fixes | What it drives in the quote |
|---|---|---|
| Sequence | The molecule: residues, order, termini, modifications | Synthesis steps, raw materials, difficulty, time |
| Purity target | The HPLC purity the lot must meet | Purification passes, yield loss, analytical time |
| Fill per vial | Peptide per vial | Total peptide mass, fill run, lyophilization |
| Quantity in kits | Vial count (1 kit = 10 vials) | Total peptide mass, vials, labels, cartons |
| Labelling | Neutral label or your artwork; carton, insert | Print, proof rounds, assembly |
| Documents | What ships beyond the batch COA | Additional testing or paperwork |
Two of the six, sequence and purity, determine the chemistry. Two, fill and quantity, determine the scale. Two, labelling and documents, determine the presentation. A buyer who understands which group a change belongs to can predict which way the number moves.
Solid-phase synthesis builds the peptide one residue at a time on a resin. Each residue added is a coupling step with its own reagents, washes and checks, so a longer sequence costs more in reagents and time roughly in proportion to its length. That part is easy to anticipate. The harder part is difficulty, which does not scale with length alone.
Some residues couple slowly or incompletely and need repeated couplings. Some stretches of sequence aggregate on the resin as the chain grows, which slows every subsequent step and lowers the yield of full-length product. Sequences rich in certain hydrophobic or branched residues, or with long runs of the same residue, are the usual suspects. The factory reads the sequence at the feasibility step and prices these effects in, which is why the quote cannot be written from the length alone.
Difficulty also affects purity before purification. A sequence that assembles cleanly gives a crude product dominated by the full-length peptide, and purification is quick. A sequence that assembles badly gives a crude product full of deletion and truncation species close in retention time to the product, and purification takes more passes to reach the same target. So difficulty appears twice in the number: once in synthesis and once in purification.
What a buyer can do: send the sequence exactly as intended, state the termini explicitly (free or modified), and avoid adding residues that the project does not need. A tag or spacer added "for convenience" is a longer, possibly harder sequence.
Purity is set by preparative HPLC. The crude peptide is injected, fractions are collected across the main peak, and the fractions that meet the target are pooled. Raising the target means keeping fewer fractions, which lowers yield, and often means a second pass, which doubles the purification time and the yield loss. The relationship between target and cost is therefore not linear: each step up costs more than the last.
For reference, published HPLC purity results across Pepti's public COA library of catalogue lots fall between 98.4% and 99.8% as of the last review date on this page. That range describes what the factory routinely achieves on its catalogue; a custom lot is reported against the target written in its own specification, and the quote reflects the target you choose.
What a buyer can do: specify the purity the project needs rather than the highest purity imaginable. If the project is a screen where minor species do not matter, a routine target is cheaper and faster. If the project requires a higher target, say so and expect the quote and the lead time to reflect the extra passes. Either way, the purity on the certificate is measured on the lot, not assumed from the target.
Fill per vial and vial count together determine the total mass of peptide the factory must make. A small fill in many vials and a large fill in few vials can need the same total mass but cost differently, because vials, stoppers, labels and the fill run itself scale with vial count while synthesis scales with mass.
On this desk the vial count is set in kits: 1 kit is 10 vials and the custom minimum is 100 kits, so the smallest custom run is 1,000 vials. At that scale the fill run and lyophilization cycle are a meaningful part of the cost, and the quote states them as part of one lot price rather than as a per-vial surcharge.
What a buyer can do: choose the fill the end use actually needs and let the kit count follow from the total quantity, rather than the other way round. Changing the fill after the quote reopens both the fill run and the label, so settle it before confirming.
Anything beyond a linear chain of the 20 standard amino acids is a modification: an acetylated N-terminus, an amidated C-terminus, a non-standard residue, a cyclization, a conjugated label or lipid, a specific salt form. Each adds reagents, steps and often a dedicated purification, and some add analytical work to confirm that the modification is present and in the right place.
Modifications are confirmed case by case at the feasibility step. The quote either includes them in writing or states that they are not included; a modification that is not written into the confirmed specification is not in the order. Do not assume that a modification common elsewhere is routine here, and do not assume the reverse; ask, and get the answer in writing before confirming.
What a buyer can do: list every modification explicitly, including "none" where that is the case, and separate the modifications the project requires from those that are merely conventional. The factory will tell you which ones change the number and by how much.
A neutral label with the sequence name, fill, lot code and research-use statement is part of the baseline. Your own artwork on the vial is a private-label option: the factory supplies template dimensions and the fixed elements that must remain, returns a proof with the lot-code position marked, and prints after you approve it. Cartons and inserts are further options with their own print and assembly cost.
Labelling affects the quote less than the chemistry does, but it affects the lead time more than buyers expect, because print waits for proof approval. Each correction round is a day or more. A custom lot typically takes 15 days from confirmation and payment; a proof that takes a week to approve does not extend the synthesis, but it can delay the shipment past the lot's completion.
What a buyer can do: send print-ready files to the template at the time of the RFQ, approve or correct in one round, and leave cartons and inserts out of the first order unless the end use needs them.
Every lot ships with a batch Certificate of Analysis carrying the HPLC purity result and the MS molecular-weight identity result, a lot-coded label and a packing list. That baseline is included in the quote. Documents beyond it, such as a report on a measurement the baseline does not cover, are written into the specification and priced there, because they usually mean additional analytical work on the lot.
What a buyer can do: ask for the documents you will actually check. The receiving checklist shows what the baseline set lets you verify; if your project needs more, say exactly what, so the factory can quote it rather than guess.
The six drivers describe how the number changes with the specification. The minimum order describes where it starts. A custom run has a fixed cost that does not depend on quantity: setting up the synthesis, running the purification method, running the fill line, issuing the certificate. Below a certain quantity that fixed cost dominates and the per-vial figure becomes unreasonable; above it the fixed cost is spread thinly enough to quote sensibly. On this desk that point is 100 kits, or 1,000 vials, for a custom sequence, and 50 kits for a catalogue private label where the synthesis has already happened. The MOQ guide works through the arithmetic in words.
The practical consequence for the quote is that the first 100 kits carry the fixed cost, and further kits of the same sequence at the same fill are quoted at a lower increment. A buyer planning a repeat order should say so at the RFQ, because a lot sized for the whole programme can be cheaper per vial than two lots a few months apart, each with its own set-up.
A quote from Pepti is written against the specification sheet and restates it, so there is one document to confirm. It contains the items in the panel. Nothing in it is a fixed promise: the lead time is the expected figure for the sequence as specified, counted from confirmation and payment, and the certificate reports what the lot measures.
If a quote from any supplier lacks the lead-time basis, the purity basis or the document list, the number on it is not comparable with a number that has them. The next section turns that into a reading checklist.
Contents of a Pepti quote
Buyers often ask what they can change to bring a quote down. The honest list, in order of effect:
What does not move the number: negotiating the fixed set-up, which is the same for every buyer; asking for a lead time shorter than the chemistry allows; or splitting an order below the minimum. The minimum is where the number starts to make sense for both sides.
The same six drivers let you read a quote from any custom-synthesis supplier and tell whether two numbers are comparable. Ask of each quote:
A quote that answers all of these is comparable with another that does. A quote that answers none of them is a number, not a quote.
Scope statement
Pepti does not present itself as a cGMP drug-substance (API) manufacturer or CDMO and does not publish a GMP certificate or DMF. Peptides on this site are supplied for research use by qualified B2B buyers. For research use only. Not for human or veterinary use.
Because a custom run is priced as a lot, not per milligram, and the lot price depends on sequence difficulty, purity target, fill, vial count, modifications and documents. A per-milligram figure without those is not comparable between quotes. Send the six specification fields and the quote is written for your sequence.
Yes, and increasingly so with each step up, because fewer fractions are kept and a second preparative pass is often needed. Specify the purity the project needs. The lot certificate reports the purity measured, whatever the target.
It is the expected lead time for the sequence as specified, counted from specification and payment confirmation; typically 15 days for a custom lot. It is stated per order and is not a fixed commitment. Feasibility notes in the quote say if the sequence is expected to take longer than typical.
A repeat of the same sequence and fill starts from the confirmed specification and the proven configuration, which saves the feasibility round and any proof round. The synthesis set-up still runs for each lot, so the biggest saving comes from sizing one lot for the programme rather than from repeating small lots.
100 kits, which is 1,000 vials of one sequence at one fill. Smaller quantities are not quoted; the MOQ guide explains why.
Open WhatsApp with a pre-filled Pepti-RFQ message, or email the same details. A quote needs the compound or sequence, fill per vial, vial count, labelling and the document set you require.