Blood sugar values are usually written in one of two unit systems: mg/dL or mmol/L. The values
can look very different even when they describe the same glucose concentration.
The basic conversion is:
mg/dL = mmol/L x 18
To convert the other direction:
mmol/L = mg/dL / 18
mmol/L to mg/dL calculator
Type a value in either field and the other one updates:
Uses the standard factor: mg/dL = mmol/L × 18. Values are rounded the way meters usually display them: whole numbers for mg/dL, one decimal for mmol/L.
That formula is the same one used by common diabetes conversion references such as the Diabetes.co.uk blood sugar converter. The math is simple, but unit confusion is still one of the easiest ways to make a log harder to trust.
mmol/L to mg/dL conversion chart
This table rounds to the nearest whole mg/dL, which is usually enough for manual logging.
| mmol/L | mg/dL |
|---|---|
| 3.0 | 54 |
| 3.5 | 63 |
| 4.0 | 72 |
| 4.5 | 81 |
| 5.0 | 90 |
| 5.3 | 95 |
| 5.5 | 99 |
| 6.0 | 108 |
| 6.4 | 115 |
| 6.5 | 117 |
| 7.0 | 126 |
| 7.8 | 140 |
| 8.0 | 144 |
| 8.5 | 153 |
| 9.0 | 162 |
| 10.0 | 180 |
| 11.0 | 198 |
| 12.0 | 216 |
| 13.0 | 234 |
| 14.0 | 252 |
| 15.0 | 270 |
If your meter and app use the same unit, you usually do not need to convert anything. The safest workflow is to keep the unit visible and avoid switching units casually.
Detailed chart for the 5.0 to 8.1 mmol/L range
Many everyday readings and reference values fall between 5 and 8 mmol/L, so this chart covers that
range in 0.1 steps. Values are rounded to the nearest whole mg/dL.
| mmol/L | mg/dL | mmol/L | mg/dL |
|---|---|---|---|
| 5.0 | 90 | 6.6 | 119 |
| 5.1 | 92 | 6.7 | 121 |
| 5.2 | 94 | 6.8 | 122 |
| 5.3 | 95 | 6.9 | 124 |
| 5.4 | 97 | 7.0 | 126 |
| 5.5 | 99 | 7.1 | 128 |
| 5.6 | 101 | 7.2 | 130 |
| 5.7 | 103 | 7.3 | 131 |
| 5.8 | 104 | 7.4 | 133 |
| 5.9 | 106 | 7.5 | 135 |
| 6.0 | 108 | 7.6 | 137 |
| 6.1 | 110 | 7.7 | 139 |
| 6.2 | 112 | 7.8 | 140 |
| 6.3 | 113 | 7.9 | 142 |
| 6.4 | 115 | 8.0 | 144 |
| 6.5 | 117 | 8.1 | 146 |
A few frequently looked-up values, written out:
6.1 mmol/Lis about110 mg/dL(109.8 before rounding).6.5 mmol/Lis117 mg/dL.6.8 mmol/Lis about122 mg/dL(122.4 before rounding).7.0 mmol/Lis126 mg/dL.7.8 mmol/Lis about140 mg/dL(140.4 before rounding).
These are unit conversions only. What any particular number means for you depends on timing, context, and your care team’s guidance — the same value reads differently fasting versus after a meal.
Why do both units exist?
mg/dL means milligrams per deciliter. It is common in the United States. mmol/L means millimoles
per liter. It is common in many other countries, including the United Kingdom.
The same clinical guidance may appear in different units depending on country. For example, the
NICE diabetes in pregnancy guideline
lists pregnancy blood glucose target examples in mmol/L. Many US-facing diabetes resources,
including American Diabetes Association materials, commonly use mg/dL.
Neither unit is more “real.” They are two ways of writing the same kind of measurement. The problem starts when a log mixes them without labeling each value.
Common conversion examples
Here are a few examples that appear often in logs and articles:
| Situation in a log | mmol/L | mg/dL |
|---|---|---|
| 5.3 mmol/L pregnancy fasting example from NICE | 5.3 | about 95 |
| 7.8 mmol/L one-hour post-meal example from NICE | 7.8 | about 140 |
| 10.0 mmol/L | 10.0 | 180 |
| 70 mg/dL written in mmol/L | about 3.9 | 70 |
| 126 mg/dL written in mmol/L | 7.0 | 126 |
The American Diabetes Association diagnosis page
uses mg/dL for diagnostic lab thresholds. A home logbook should not diagnose anything from those
thresholds, but the page is a useful example of why unit labels matter when numbers move between
medical references and personal records.
What if the converted number has decimals?
When converting from mg/dL to mmol/L, decimals are normal. For example:
95 mg/dL / 18 = 5.3 mmol/L126 mg/dL / 18 = 7.0 mmol/L180 mg/dL / 18 = 10.0 mmol/L
Many meters that use mmol/L show one decimal place. Many meters that use mg/dL show whole
numbers. That difference is expected. Do not add extra precision to a paper log just because a
calculator produced a longer decimal.
Do not convert the same entry twice
Most unit mistakes happen when a value moves between places: meter, notes app, spreadsheet, portal, or a printed handout. If you convert a value for a report, keep the original unit visible somewhere in the record. That makes it easier to spot a copy mistake later.
For example, if your meter reads 7.8 mmol/L, the converted value is about 140 mg/dL. Do not then
treat 140 mg/dL as if it were an original mmol/L value and multiply again. A simple note like
“converted from 7.8 mmol/L” is enough when you need both systems in the same document.
If you are not sure which unit your meter uses, check the meter display, the box, or the companion app settings before entering a backlog of readings. Fixing the unit at setup is much easier than cleaning up a mixed-unit log later.
How to avoid unit mistakes in a manual log
Use a few simple habits:
- Pick the unit that matches your meter and clinician paperwork.
- Write
mg/dLormmol/Lnext to every value. - Avoid copying values into a notes app without the unit.
- If you convert a value, mark it as converted.
- Use one unit consistently in reports unless your clinician asks for both.
The free printable blood sugar log template includes a unit field so paper entries stay explicit. Vakaa does the same thing on iPhone: the selected unit stays visible next to readings and reports.
How Vakaa handles units
Vakaa supports mg/dL and mmol/L for manual blood sugar logging. The app is still a logbook, not a
meter or a medical device. It records the reading you enter, keeps timing context attached, and
makes later review easier.
If you are setting up a new log, choose the unit that matches your meter. If you are logging for pregnancy, read the guide to pregnancy blood sugar targets and confirm your target numbers with your care team. If you want a broader logging workflow, start with the guide to keeping a blood sugar log on iPhone.