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Units to mg converter

Convert between syringe units, mL, mg and mcg for the concentration on your vial. Works for U-100, U-50 and U-40 scales, in both directions.

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A units to mg converter uses your vial's concentration to translate insulin syringe units into mL, mg and mcg (and back), because a syringe unit measures volume, not an amount of drug.

Units ⇄ mL ⇄ mg converter

Pick the syringe in your hand (check the U- number and size on the box), enter your vial's concentration from its label, then the number you want to convert.

Your syringe

U-100 units

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Volume

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Amount

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Math only, not dosing advice. Follow your prescriber or label.

Save your vial in Caliper and it remembers the concentration you entered, alongside your dose log. The converter above is a browser tool and is not part of the app.

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How units, mL and mg relate

A "unit" on an insulin syringe is a volume. The U- number says how many units make 1 mL: 100 on a U-100 syringe (1 unit = 0.01 mL), 50 on a U-50 (0.02 mL) and 40 on a U-40 (0.025 mL). An amount in mg or mcg only comes in when you multiply that volume by the vial's concentration.

  • mL = units ÷ units per mL
  • mg = mL × concentration (mg/mL)
  • mcg = mg × 1,000
  • Going back: mg ÷ concentration = mL, then mL × units per mL = units

Math-only example, made-up numbers:20 units on a U-100 syringe is 0.2 mL. At 5 mg/mL that's 1 mg (1,000 mcg). The same 20 marks on a U-40 syringe would be 0.5 mL, or 2.5 mg at the same concentration, which is why the scale matters.

Your concentration comes from the pharmacy label (often printed as mg/mL) or, for a vial you mixed, from the reconstitution calculator.

FAQ

How do I convert syringe units to mg?
Convert units to mL first (divide by 100 on a U-100 syringe, 50 on U-50, 40 on U-40), then multiply the mL by the vial's concentration in mg/mL. For example, 20 units on a U-100 syringe is 0.2 mL; at 5 mg/mL that holds 1 mg. Math only, not a dose suggestion.
How many units are in 1 mL?
100 on a U-100 syringe, 50 on a U-50 syringe and 40 on a U-40 syringe. Check the scale printed on the box and barrel.
Why can't I convert units to mg without a concentration?
A unit on a syringe is a volume. How many mg are in that volume depends entirely on how concentrated the liquid is, so the same number of units means different amounts in different vials.
How do I convert mg to units?
Divide the amount in mg by the concentration in mg/mL to get mL, then multiply by the syringe's units per mL (100 for U-100).
Is a U-50 syringe the same as a 0.5 mL insulin syringe?
Usually not. Most 0.5 mL insulin syringes are U-100 syringes that hold 50 units. A U-50 scale means 50 units = 1 mL. Read the U- number on the package.
Is anything I type saved or sent?
No. The math runs in your browser. We record only that the converter was viewed or used and whether its button was clicked, never the numbers or results.

Related guides

For adults 18+. Educational math only, not medical advice. This tool does not recommend any dose, dilution, syringe or compound. Always follow your prescriber's instructions and the product label, and ask a pharmacist if a number doesn't look right.