Insulin syringes are marked in "units," not mL — and U-100 and U-40 syringes read differently for the exact same volume. This tool converts either way, instantly. For a full dose-to-units conversion, see the mg to Units Calculator.
Units ⇄ mL converter
A one-off calculation — nothing here is saved or sent anywhere.
How to Use This Calculator
Two inputs and a direction toggle — built for a quick mid-protocol check.
Pick your syringe typeU-100 is the most common insulin syringe for small subQ peptide doses; U-40 is common for some veterinary and older insulin products.
Choose a direction"Units → mL" if you're reading a syringe and want the actual liquid volume; "mL → Units" if you have a target volume and want to know where that lands on your syringe.
Enter your numberType the units or mL value you're starting from.
Read the converted valueThe result updates instantly as you type — no submit button needed.
How the Math Works
Straightforward unit conversion based on fixed syringe manufacturing standards — not a clinical calculation.
The relationship is fixed by the syringe, not the drug. A U-100 syringe is manufactured so that 100 unit-marks span exactly 1 mL of barrel volume; a U-40 syringe spans 40 unit-marks per mL. This is true regardless of what's inside — units on a syringe describe a graduation scale, not a drug quantity. ISO 7864 sterile hypodermic needle and U-100/U-40 syringe graduation standards.
Units → mL. mL = units ÷ units-per-mL for the selected syringe type. Direct algebraic inverse of the syringe's graduation ratio.
mL → Units. units = mL × units-per-mL for the selected syringe type. Same relationship, applied in the other direction.
Estimate only — not medical advice. This is a unit-conversion tool only. It does not evaluate whether a given volume or unit reading is an appropriate dose for you. Confirm your protocol with a licensed clinician or pharmacist.
Frequently Asked Questions
Why do U-100 and U-40 syringes give different numbers for the same volume?
Because "units" is a graduation scale printed on the syringe barrel, not a fixed measure of liquid. A U-100 syringe crams 100 unit-marks into 1 mL of space; a U-40 syringe spreads only 40 unit-marks across that same 1 mL. The same 0.25 mL reads as 25 units on a U-100 syringe but 10 units on a U-40 syringe.
Which syringe type should I use?
Use whichever syringe type matches what your product or prescriber specifies. Insulin products are commonly labeled for a specific syringe standard (U-100 is by far the most common in the US today), and mismatching syringe and product labeling is a well-documented dosing-error risk.
What is a "standard mL-marked" syringe?
Some syringes (often used for small research or compounded doses) are marked directly in mL or fractions of a mL rather than in insulin "units." Selecting that option in this tool treats 1 "unit" as literally 1 mL, so the conversion becomes a pass-through — useful if your syringe has no units concept at all.
Can I use this for a dose in mcg or mg instead of a volume?
This tool converts pure units-to-volume. If you're starting from a dose amount rather than a volume, use the mg to Units Calculator, which factors in your concentration first.
Why is my converted number not a whole unit?
Real doses and syringe capacities don't always land on clean numbers. A fractional unit reading (like 23.7) may be accurate but harder to draw precisely — some people round to their syringe's finest visible gradation, which is worth discussing with whoever supplied your syringes.
Does the syringe barrel size (0.3 mL vs 1 mL) matter for this conversion?
No — this conversion is about the units-per-mL graduation standard (U-100 vs U-40 vs plain mL), not the total barrel capacity. A 0.3 mL U-100 syringe and a 1 mL U-100 syringe both read 100 units per mL; they just hold different maximum volumes.
Is this the same as the Reconstitution Calculator?
No — the Reconstitution Calculator works out concentration from your vial size and BAC water and then converts a dose all the way to units. This tool is a narrower, faster pure unit converter for when you already have a units or mL number in hand.
Does this tool save or send my numbers anywhere?
No. Everything runs locally in your browser and nothing is stored or transmitted. To track your actual dose history over time, see the full Peptide Plug app.
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