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Blood Sugar Converter

Health

Convert blood glucose readings between mg/dL and mmol/L instantly using the standard 18.0182 conversion factor — accurate for US and international units.

Reviewed by the thecalcu.com team · Last updated July 4, 2026

Convert
Blood Glucose Value (mg/dL)
mg/dL

Converted Value

0mmol/L

Reference Range (Fasting)

Prediabetes range (fasting)

Based on ADA fasting glucose guidelines: Normal <100 mg/dL, Prediabetes 100-125 mg/dL, Diabetes ≥126 mg/dL. This is informational only, not a diagnosis.

What is a Blood Sugar?

A blood sugar converter translates blood glucose readings between the two units used worldwide: mg/dL (milligrams per deciliter), the standard in the United States, and mmol/L (millimoles per liter), used across most of Europe, Canada, Australia, and elsewhere. Both units measure the exact same physical quantity, glucose concentration in your blood, expressed on different scales, using the precise molar mass of glucose (18.0182 g/mol) as the conversion factor.

This becomes essential whenever you're comparing readings from sources that use different units, an imported glucose meter, medical records from another country, or international guidelines written in mmol/L when your own device reports mg/dL. Getting the conversion right matters for correctly reading whether a value falls in a normal, prediabetic, or diabetic range, so pairing this with the Diabetes Risk Calculator can add useful additional context.

Who Should Use This Calculator?

People managing diabetes or prediabetes whose glucose meter reports a different unit than their doctor uses.

International travelers managing diabetes who need to interpret readings in an unfamiliar unit system while abroad.

Caregivers helping a family member make sense of glucose readings from records in a different unit.

Healthcare students who need quick, accurate conversions for coursework or patient education.

Anyone reading international diabetes research or guidelines published in mmol/L when they're more used to mg/dL, or the other way around.

How to use this Blood Sugar calculator

  1. Choose your conversion direction, mg/dL → mmol/L or mmol/L → mg/dL.
  2. Enter your Blood Glucose Value in the starting unit.
  3. Review the Converted Value shown in the result card.
  4. Repeat with additional readings to compare multiple test results across units.
  5. Cross-check any borderline result with your healthcare provider rather than relying on the conversion alone to interpret what it means.

Common Mistakes to Avoid

Converting in the wrong direction. It's easy to accidentally leave the direction toggle on the previous setting, double-check it's set to match the unit your reading is actually in before trusting the result.

Rounding the conversion factor to a flat 18. It's close enough for a quick mental estimate, but this converter uses the precise 18.0182 figure, which matters if you're comparing a value against a clinical reference range with a tight threshold.

Treating a converted value as a diagnosis. A converted number tells you the same reading in different units, it doesn't tell you what that number means for your health. Reference ranges are general population guidelines, not a personal medical assessment.

Mixing up fasting and postprandial reference ranges. The conversion math is identical either way, but a "normal" mg/dL or mmol/L range for a fasting reading is different from a normal range for a reading taken after a meal, check which context applies before comparing your number against a threshold.

Quick Reference

mg/dL mmol/L Typical context
70 3.9 Lower hypoglycemia threshold
100 5.6 Normal fasting upper limit
126 7.0 Diabetes fasting threshold
200 11.1 Diabetes random-test threshold

Related tools: the A1c Calculator for longer-term average glucose, the Diabetes Risk Calculator for a broader risk assessment beyond a single reading, and the BMR Calculator if diet and metabolism factors are part of what you're tracking alongside glucose.

Show formula & methodology ↓Show less ↑

Formula & Methodology

mg/dL → mmol/L: mmol/L = mg/dL ÷ 18.0182

mmol/L → mg/dL: mg/dL = mmol/L × 18.0182

Worked example: converting a fasting reading of 95 mg/dL to mmol/L:

95 ÷ 18.0182 ≈ 5.27 mmol/L

That falls within the normal fasting range of below 100 mg/dL (5.6 mmol/L) per ADA guidelines, for informational reference only, not a diagnosis.

Frequently Asked Questions

What's the formula to convert mg/dL to mmol/L?
Divide the mg/dL value by 18.0182 to get mmol/L, 100 mg/dL comes out to approximately 5.55 mmol/L. This conversion factor comes from the molar mass of glucose, 180.16 g/mol, and it's the internationally standardized figure used in clinical settings.
What's the formula to convert mmol/L to mg/dL?
Multiply the mmol/L value by 18.0182 to get mg/dL, 5.5 mmol/L comes out to approximately 99.1 mg/dL. It's simply the inverse of the mg/dL-to-mmol/L conversion.
Why do different countries use different blood sugar units?
The United States primarily uses mg/dL (milligrams per deciliter), while most of Europe, Canada, Australia, and many other countries use mmol/L (millimoles per liter) as the standard clinical unit for blood glucose. Both measure the exact same underlying quantity, glucose concentration in blood, just expressed on different scales.
What's considered a normal fasting blood sugar level?
Per American Diabetes Association guidelines, a normal fasting blood glucose level sits below 100 mg/dL (5.6 mmol/L). Levels between 100 and 125 mg/dL (5.6–6.9 mmol/L) fall in the prediabetes range, and 126 mg/dL (7.0 mmol/L) or higher on two separate tests indicates diabetes. This is general reference information, not a diagnosis, always interpret your own readings with a healthcare provider.
Is this converter accurate enough for medical decisions?
The math itself is precise, using the standard 18.0182 factor, but this is an informational conversion tool, not a diagnostic device. Always work from your glucose meter's actual reading and consult a healthcare provider for medical interpretation and decisions.
Why is the conversion factor 18.0182 and not a round 18?
18.0182 is glucose's precise molar mass in g/mol, and using this exact figure produces a more accurate conversion than the commonly rounded factor of 18. For casual, everyday purposes, 18 gets you close enough, but 18.0182 gives clinical-grade precision.
What blood sugar reading indicates hypoglycemia?
Hypoglycemia, or low blood sugar, is generally defined as a reading below 70 mg/dL (3.9 mmol/L), though symptoms and thresholds vary by individual, especially for people on insulin or certain diabetes medications. Severe hypoglycemia requiring immediate treatment is typically below 54 mg/dL (3.0 mmol/L).
My meter shows one unit but my doctor's chart uses the other, how do I compare them?
Enter your meter's reading using the correct starting unit and this converter shows the equivalent instantly, so you can compare it against a reference range or a doctor's notes regardless of which unit they're written in.
Does A1C use the same units as a blood sugar reading?
No, A1C (glycated hemoglobin) is reported as a percentage reflecting average blood sugar over roughly 2–3 months, a fundamentally different measurement from a single-point mg/dL or mmol/L glucose reading. This converter handles point-in-time glucose unit conversion specifically, not A1C, for that, see the [A1c Calculator](/a1c-calculator/).
Can I convert a postprandial (after-meal) reading the same way?
Yes, the mg/dL to mmol/L conversion factor stays the same regardless of whether the reading is fasting, postprandial, or random. Only the reference ranges used to interpret what counts as 'normal' change depending on when the reading was taken.
What is 200 mg/dL in mmol/L?
200 mg/dL converts to approximately 11.1 mmol/L (200 ÷ 18.0182), a level generally considered diagnostic of diabetes when found on a random blood glucose test alongside symptoms, though a formal diagnosis always requires a healthcare provider's evaluation.
Also known as
mg/dL to mmol/L converterblood glucose unit converterglucose converterblood sugar unit conversionmmol to mg/dL