Insulin syringe units to mL

On a U-100 scale, 100 units sit in 1 mL — so 30 units is 0.30 mL and 50 units is 0.50 mL. On a U-40 scale, 40 units sit in 1 mL, and those same 30 units become 0.75 mL. The unit mark is not a volume. The scale printed on the barrel is what decides.

UltiMed publishes both calibrations on its VetRx family page: a U-40 barrel is graduated at 40 units per mL, a U-100 barrel at 100 units per mL. Everything in the table below follows from those two figures, or is quoted from a product listing that prints a capacity and a unit count together.

What each unit mark is worth in mL

Unit mark on the barrel	Volume on a U-100 scale	Volume on a U-40 scale	Source of the row
1 unit	0.01 mL	0.025 mL	Both computed here from the stated calibrations (UltiMed)
2 units	0.02 mL	0.05 mL	Both computed, same basis
5 units	0.05 mL	0.125 mL	Both computed, same basis
10 units	0.10 mL	0.25 mL	Both computed, same basis
15 units	0.15 mL	0.375 mL	Both computed, same basis
20 units	0.20 mL	0.50 mL	U-100 computed; U-40 quoted — Banfield lists the U-40 1/2 cc (ml) barrel with whole unit markings at 20 units
25 units	0.25 mL	0.625 mL	Both computed, same basis
30 units	0.30 mL	0.75 mL	U-100 quoted — Banfield lists the U-100 3/10 cc (ml) barrel at 30 units; U-40 computed
40 units	0.40 mL	1.00 mL	U-100 computed; U-40 quoted — Banfield lists the U-40 1 cc (ml) barrel at 40 units
50 units	0.50 mL	—	U-100 quoted — Banfield lists the U-100 1/2 cc (ml) barrel at 50 units; no U-40 barrel in these sources carries a 50-unit mark
100 units	1.00 mL	—	U-100 computed; no U-40 barrel in these sources carries a 100-unit mark

Four cells above are quoted rather than calculated, and all four come from Banfield's two product listings, which print a millilitre capacity and a unit count in the same sentence. The rest is arithmetic on 100 units per mL and 40 units per mL. That includes 1 mL = 100 units, which is the most obvious figure on the page and which none of the sources here actually prints.

The U-40 column stops at 40 units for a reason. The largest U-40 barrel in these sources is 1 cc, listed at 40 units. A U-40 barrel carrying a 50- or 100-unit mark is not in evidence, so those cells are dashes.

Which marks the barrel actually carries

A computed millilitre value is not a promise that the barrel has a line there. UltiMed's 1.0 mL U-100 syringe is "graduated in 2-unit increments" — it carries no 1-unit line, so 0.01 mL is a conversion rather than something readable off that barrel.

Nominal capacity	Graduation interval	Numbering	Source and status
0.3 mL, U-100	"graduated in 1-unit increments"	Numbered every 5 units	Interval quoted (UltiMed); numbering quoted as reproduced in MSF's procurement specification, and independently in FDA 510(k) K193273
0.5 mL, U-100	"graduated in 1-unit increments"	Numbered every 5 units	As above
1.0 mL, U-100	"graduated in 2-unit increments"	Numbered every 10 units	As above
0.3 mL, U-100 half-unit variant	"½ unit scale marking available on the 0.3mL barrel"	—	Quoted (Embecta Corp.); a separate SKU at Allison Medical — item 22-6504, footnoted "*HUM - Half Unit Markings", against 22-6503 on the same 31G × 5/16" 3/10cc barrel
0.3 mL and 0.5 mL, U-40 half-unit variants	"Half Unit Scale" / "1/2 unit scale mark"	—	Quoted (VetRxDirect; Prime Dental & Medical Supply; UltiMed product 82001, "HALF-UNIT MARKINGS: Dose unit markings in half-unit increments…")
U-40, whole-unit products	"Whole unit markings on syringe"	Not stated by any source consulted	Quoted (Banfield); no numeric interval for a whole-unit U-40 barrel appears in the sources below

mL to units, read the other way

Same table, reversed. A 0.3 mL barrel reads to 30 units on a U-100 scale (quoted, Banfield) and 12 units on a U-40 scale (computed). A 0.5 mL barrel reads to 50 units U-100 (quoted) and 20 units U-40 (quoted). A 1 mL barrel reads to 100 units U-100 (computed) and 40 units U-40 (quoted). The barrel is the same volume in every case; only the printed scale changes.

Why the scale, not the barrel, decides the answer

The capacity and the scale are two separate fields on the same product. Federal device records make that plain: Becton, Dickinson registers a device whose brand name is literally "BD Pet Syringes, 0.3mL x 12MM U-40" — the millilitre capacity and the U-40 designation sitting side by side as distinct attributes. EXELINT does the same in catalogue form, where all eleven insulin syringe item descriptions lead with "U-100" ahead of the gauge: 26010 is "U-100 31G x 5/16"", 26018 is "U-100 29G x 1/2"". The scale is part of what identifies the SKU.

MSF's procurement specification for a U-100 insulin syringe states the design rule behind that, as reproduced from ISO 8537: "The syringe scale shall be graduated in increments corresponding to units of only one concentration of insulin." The same document reproduces the requirement that "The barrels of syringes shall be marked with the insulin concentration for which the syringe was designed to hold, e.g. the text "U-100 insulin" ("units" or "I.U.")", that "The nominal capacity of the syringe shall be designated in millilitres (ml)", and that the syringe indicates its intended concentration through visual and non-visual means. Two numbering systems, one barrel size, printed separately.

That is why one calibration figure cannot be treated as a fact about syringes generally. Embecta's US Ultra-Fine range publishes a separate U-500 syringe with a green U-500 symbol and a green needle shield — a third scale, shipping as a product. And Banfield's own catalogue carries the contradiction cleanly: 0.5 mL of barrel is 50 units on its U-100 listing and 20 units on its U-40 listing, in identical wording, one vendor, same page furniture. VetRxDirect states it flatly on its U-40 page: "U-40 syringes and U-100 syringes are NOT the same." And: "U-40 syringes and U-100 syringes are NOT interchangeable."

Distinguishing near-identical variants comes down to two printed attributes. Allison Medical's CarePoint Vet sheet lists 12-4910 and 12-7910 as separate item numbers for what is otherwise the same 29G × 1/2" 1cc barrel, because one is U-40 and the other U-100 — the matched pairs are laid out on our U-100 vs U-40 insulin syringes page. The second attribute is the finest mark: on Allison Medical's SureComfort sheet, 22-6503 and 22-6504 are both 31G × 5/16" 3/10cc, and the only difference is the half-unit scale on 22-6504, which carries its own item number and its own NRC. UltiMed's half-unit U-40 syringe, product 82001, is likewise a distinct catalogue number from the whole-unit 3/10cc. What the markings themselves mean is covered on how to read an insulin syringe.

One caution on the graduation figures. UltiMed publishes 1-unit increments at 0.3 mL and 0.5 mL and 2-unit at 1.0 mL, for its own products. MSF's reproduction of the standard gives permitted ranges instead — 0.5 IU or 1 IU at 0.3 ml, 1 IU at 0.5 ml, 1 IU or 2 IU at 1.0 ml — so a 1 mL barrel from another maker may be finer than UltiMed's. The MSF graduation table is headed "graduation scales for U-100 insulin syringes" and covers that scale only; no numeric graduation interval for a whole-unit U-40 barrel appears in any source consulted here, which is why the U-40 row above quotes a phrase and not a number.

Where to buy

UltiMed's 1 mL/cc 29G × 12.7mm U-100 syringe, manufacturer product number 09219, is listed on Amazon: UltiCare U-100 Insulin Syringes, 1cc, 29G x 12.7mm, 100 count.

Non-Amazon listings exist for the veterinary U-40 products. Banfield lists the UltiCare VetRx U-40 whole-unit 100-count box, and VetRxDirect lists the BD/Embecta U-40 half-unit boxes in 3/10mL and 1/2mL. Prime Dental & Medical Supply lists BD 323000 and marks it "Item Discontinued." Prices move; the links below were read on 2026-08-01.

Sources

Specifications last verified: 2026-08-01