Keel · Guides · Tools

Use the Syringe Units converter

Convert between millilitres and syringe units for the syringe you use, and see the draw on a drawn barrel — arithmetic on your own numbers, saved nowhere.

Written for Keel 1.0.0Guides v1Screens from build 1 (4cbadaa)

Before you begin

The screen is titled Syringe Units with the line "Convert between milliliters and syringe units for your syringe scale." Under Your values: a direction switch and up to three fields. Under Your syringe: a barrel picker and a drawing.

There is no error copy on this screen; what appears depends on what parses: the result card needs the first field and a Syringe scale above zero; the drawing needs only a volume in mL → units mode, or the result in units → mL mode; Concentration never gates either.

Keel tracks. It never advises. This converter multiplies or divides the numbers you enter; nothing here suggests an amount, a syringe, or a concentration.

Steps

Open Tools › Calculators › Syringe Units.
Choose the direction: mL → units or units → mL.
Enter the first field: Volume (mL) in mL → units mode, or Units in units → mL mode. It has no presets.
Set Syringe scale in units/mL — it starts at 100. The chips 30, 50, 100 are shortcuts only if that is the scale already printed on your syringe.
Optional: enter Concentration in mg/mL to also see what that volume holds; its chips are shortcuts only for a value already on your vial’s label.
Read the result card: SYRINGE UNITS (a bare number) in mL → units mode, or VOLUME ("n mL") in units → mL mode; with a concentration, a row That volume holds "n mg". The footer reads "Calculated from your values."
Under Your syringe, pick the barrel: 0.3 mL · 30 u, 0.5 mL · 50 u, 1 mL · 100 u, 3 mL or 5 mL; the 1 mL · 100 u barrel is selected by default. The number is the barrel’s capacity — all three insulin barrels are printed at 100 units per mL.
Read the drawing: the callout chip at the fluid line reads "n u" on the insulin barrels and "n mL" on the 3 mL and 5 mL barrels; the row On this syringe repeats the reading.

What it looks like

Syringe Units screen in mL to units mode with Volume 0.35 mL, scale 100 units per mL, and a result card reading Syringe units 35. — Fictional example: a volume and a syringe scale, and the units Keel computes from them — nothing here is a suggested amount.
direction
Volume
Syringe scale
SYRINGE UNITS
Fictional example. The values are the app’s own sample inputs, shown to explain how the fields relate; they are not a preparation or a recommendation.

The Your syringe section with the 1 mL barrel selected, the drawn syringe about 35 percent full with a 35 u callout, and an On this syringe row reading 35 units. — The same draw on a 1 mL syringe: the callout marks 35 u on the barrel and the reading row repeats it.
barrel picker
callout chip
On this syringe

The Your syringe section with the 0.3 mL barrel selected, the barrel drawn full with a 30 u callout, the reading row still 35 units, and an orange warning that the draw is more than this syringe holds. — When a draw is larger than the chosen barrel, the drawing fills completely and Keel says so; the reading row keeps the true number.
barrel picker
warning

What you’ll see

Numbers show up to two decimals, never rounded to a syringe mark. The result card uses the Syringe scale you entered; the drawing and On this syringe always use the barrel’s own scale (100 units per mL on the insulin barrels, millilitres on the others), so the two differ when your scale isn’t 100.

A draw larger than the barrel fills the drawing to the top, keeps the true number in the reading row, and shows the warning; an exactly full barrel is not flagged.

Notes and troubleshooting

No result card? Syringe scale is empty or zero, or the first field is empty (a first field of 0 still gives a result of 0). The drawing alone can still show in mL → units mode.
Type plain numbers with one decimal separator (dot or comma); the field keeps digits and the first separator only. One ambiguity to know: a number with exactly three digits after the separator and at most three before it, such as 0.125, is read as a grouped whole number (125) even though the field shows 0.125 — check that the result matches what you meant.
From Your Routine (Pro) can open this converter with the routine’s concentration prefilled — "everything stays editable, and nothing is written back."

The Oil-Based Calculator (coming later)

Where these screens come from

g4-f1 — G4-F1.png from Keel-V1-4cbadaa-guide-figures-B-20260910-165828-62385; package seal df48d7c70fb742b308677bf5d03a694f9122cc628b75451b9814645da1b37b52; source 1ffc6b52acac71a7b33212d4d251cd17ea8c1e1b8117201c6bc2be6af4626a6a; figure edd109cb2450794cf10a8e10d0f56955547857e206e7f85d348c87b6a49b94be
g4-f1b — G4-F1b.png from Keel-V1-4cbadaa-guide-figures-B-20260910-165828-62385; package seal df48d7c70fb742b308677bf5d03a694f9122cc628b75451b9814645da1b37b52; source 050e99baf849011a52551efa3c39fd5609b67dfa4298a1ddb2d3cb051214699e; figure 7ecaf6105012bacdb56ea2bdc8cf3a03a930837a58c1f17a7288b9a63d2075dc
g4-f2 — G4-F2.png from Keel-V1-4cbadaa-guide-figures-B-20260910-165828-62385; package seal df48d7c70fb742b308677bf5d03a694f9122cc628b75451b9814645da1b37b52; source d0c53fbe1a72b78ca9cdc80f8e3a61039aa2593a643f7cdafaf24253bc78a159; figure 29fc3bcd18058129b8c68b7832f2e34f37089a9e4cdceea2c9ec3b6e1a098034