# 0.3 mL, 0.5 mL and 1 mL syringes: how to read the units > How U-100 insulin syringe sizes compare, what each line is worth on a 0.3 mL, 0.5 mL and 1 mL syringe, and how to pick the one that fits a volume. Source: https://peptidetracks.com/guides/insulin-syringe-sizes-and-units Last updated: 2026-10-08 **All three sizes use the same scale: 1 unit is 0.01 mL on any U-100 syringe.** A 0.3 mL syringe holds 30 units, a 0.5 mL holds 50 and a 1 mL holds 100. What changes is how much each printed line is worth, so a smaller syringe lets you read a small volume more precisely. ## The three sizes side by side | Syringe | Holds | Typical line spacing | Reads well for | | --- | --- | --- | --- | | 0.3 mL | 30 units | 1 unit, some have half-unit lines | Volumes under 30 units | | 0.5 mL | 50 units | 1 unit | Volumes of 30 to 50 units | | 1 mL | 100 units | 2 units | Volumes of 50 to 100 units | Line spacing varies by brand. Check the barrel of the syringe in your hand before you rely on it: count the lines between two printed numbers. ## The same volume on each syringe Ten units is 0.1 mL whichever syringe you use. It is the same amount of liquid; it only looks different. | Volume | 0.3 mL syringe | 0.5 mL syringe | 1 mL syringe | | --- | --- | --- | --- | | 0.05 mL | 5 units, on a line | 5 units, on a line | 5 units, between two lines | | 0.10 mL | 10 units | 10 units | 10 units | | 0.25 mL | 25 units | 25 units | 25 units, between two lines | | 0.40 mL | Does not fit | 40 units | 40 units | | 0.80 mL | Does not fit | Does not fit | 80 units | ## Why the small syringe is easier to read On a 1 mL syringe with 2-unit lines, an odd number such as 7 units falls between two lines and has to be judged by eye. On a 0.3 mL syringe with 1-unit lines, 7 units sits exactly on a line. The barrel is also narrower, so each unit takes up more length and small differences are easier to see. ## Units are volume, not amount The unit marks tell you how much liquid is in the syringe. How much substance that liquid contains depends on the concentration: **mcg in the syringe = units × concentration (mcg/mL) ÷ 100** At 2,500 mcg/mL, 10 units contains 250 mcg. At 5,000 mcg/mL, the same 10 units contains 500 mcg. The [mcg to units converter](https://peptidetracks.com/tools/mcg-to-units-converter) does this in both directions, and the [reconstitution calculator](https://peptidetracks.com/tools/peptide-reconstitution-calculator) lets you pick the syringe size and shows the fill on the barrel. ## U-100 and U-40 are different scales Everything above applies to U-100 syringes, which are by far the most common. A U-40 syringe is graduated at 40 units per mL, so its marks mean something different. Check the barrel says U-100 before using any of these numbers. ## Common questions ### How many units is 0.5 mL? 50 units on a U-100 syringe. ### Is 10 units on a 0.3 mL syringe the same as 10 units on a 1 mL syringe? Yes. Both are 0.1 mL. ### Which syringe should I use? Use the one your pharmacist or prescriber supplied or recommended. As a matter of arithmetic, the smallest syringe that holds the full volume gives the finest scale. ### Where do I record which syringe I used? A note on the dose entry is enough. [PepVault's dose log](https://peptidetracks.com/features/dose-log) has a notes field on every entry and shows the unit on each amount. --- ## About PepVault PepVault is a free peptide tracker app for Android, iPhone, iPad and Mac. It keeps a personal log of doses, vial inventory, injection sites, schedules and reminders, body measurements and side effects, and exports the history as a CSV file. - Website: https://peptidetracks.com - Android (Google Play): https://play.google.com/store/apps/details?id=pepvault.peptide.tracker - iPhone, iPad and Mac (App Store, listed as PeptideMate - Peptide Tracker): https://apps.apple.com/us/app/peptidemate-peptide-tracker/id6814232280 PepVault is for personal record keeping. It does not give medical advice or recommend doses.