Boundary: 100 mg/dL → mmol/L
- Convert
- Glucose mg/dL → mmol/L
- Glucose
- 100 mg/dL
- Result
- 5.55 mmol/L
- If this is a fasting reading (ADA)
- Prediabetes
Checked against: 100 / 18.016 = 5.5506; ADA fasting 100–125 mg/dL is prediabetes
Blood sugar converter (mg/dL to mmol/L)
Glucose from mg/dL to mmol/L and back, and HbA1c to estimated average glucose (eAG) and IFCC mmol/mol, with ADA categories.
By AdminDrafted with AI writing toolsUpdated Checked examples: 7
Result
mmol/L
Result: 5.55 mmol/L
- If this is a fasting reading (ADA)
- Prediabetes
Informational only. Diagnosis uses laboratory plasma glucose or HbA1c tests, repeated, not a converter.
100 mg/dL is 5.55 mmol/L using 18.016 mg/dL per mmol/L; as a fasting reading it falls in the “Prediabetes” band.
Where a fasting reading sits
How it's calculated S
Divide by the factor
Why this factor
Glucose weighs 180.16 g/mol, so 1 mmol/L is 18.016 mg/dL. The other common choice is 18 (a rounded factor many meters use); the two differ by less than 0.1 %.
Fasting category
As a fasting reading, 100 mg/dL is “Prediabetes” (ADA: < 70 low, 70–99 normal, 100–125 prediabetes, ≥ 126 diabetes range).
About the blood sugar converter
Glucose converts between units through its molar mass: 1 mmol/L is 18.016 mg/dL (180.16 g/mol ÷ 10), which many meters and tables round to 18. HbA1c converts to estimated average glucose (eAG) with the ADAG regression, eAG in mg/dL = 28.7 × A1c − 46.7, and to IFCC units in mmol/mol with the NGSP–IFCC master equation. Results are placed in the American Diabetes Association (ADA) categories.
People use it to read results reported in the other unit, such as a US meter against a UK lab report. 100 mg/dL is 5.55 mmol/L, the fasting level where ADA's prediabetes range begins, and an HbA1c of 7 % corresponds to an eAG of 154 mg/dL (8.6 mmol/L) and 53 mmol/mol.
The categories are population thresholds for laboratory tests confirmed by repeat testing, not for a single meter reading. eAG is a regression estimate (R² = 0.84 in the 507-person ADAG study), so an individual's measured average can differ, and anaemia or haemoglobin variants can distort HbA1c.
How to convert mg/dL to mmol/L
Divide a glucose value in mg/dL by 18.016 to get mmol/L, or multiply mmol/L by 18.016 to get mg/dL. The factor is glucose's molar mass, 180.16 g/mol, divided by 10; many meters round it to 18. So 100 mg/dL is 5.55 mmol/L and 7.0 mmol/L is about 126 mg/dL. It applies to glucose only.
Glucose cut-offs in both units
These are the American Diabetes Association thresholds (Standards of Care 2026), converted with 18.016:
- 54 mg/dL = 3.0 mmol/L: below this is level 2 hypoglycemia
- 70 mg/dL = 3.9 mmol/L: below this is level 1 hypoglycemia
- 100 mg/dL = 5.6 mmol/L: fasting prediabetes starts
- 126 mg/dL = 7.0 mmol/L: the fasting diabetes range starts
- 140 mg/dL = 7.8 mmol/L: prediabetes starts 2 hours into a 75 g glucose tolerance test
- 200 mg/dL = 11.1 mmol/L: the diabetes range starts on that 2-hour test
The hypoglycemia levels are defined for people treated for diabetes. Below 70 mg/dL (3.9 mmol/L) is low blood sugar; treat it as your care plan says.
Factor 18 or 18.016?
The two factors differ by less than 0.1%, which matters only right at a cut-off. 7.0 mmol/L is 126.11 mg/dL with 18.016 and 126 mg/dL with 18; both reach the 126 mg/dL threshold.
Use one factor throughout, and keep it when you compare old and new readings. The factor is for glucose only; cholesterol and other substances use their own.
What a fasting reading means
ADA's fasting categories are below 100 mg/dL normal, 100–125 mg/dL prediabetes and 126 mg/dL or more the diabetes range. A diabetes diagnosis needs laboratory plasma glucose or HbA1c tests, repeated to confirm, not a single meter reading.
The fasting cut-offs apply only to a fasting test. NIDDK explains how fasting, random and glucose tolerance tests differ.
How to convert HbA1c to average glucose
The ADAG study (Nathan 2008) fitted estimated average glucose (eAG) in mg/dL = 28.7 × HbA1c − 46.7. An HbA1c of 7% gives 28.7 × 7 − 46.7 = 154.2 mg/dL, or 8.6 mmol/L.
Dividing that line by 18 gives the mmol/L form, eAG = 1.5944 × HbA1c − 2.594. To go back, HbA1c = (eAG in mg/dL + 46.7) ÷ 28.7, so an average of 126 mg/dL corresponds to 6.02%.
HbA1c in IFCC units (mmol/mol) comes from the NGSP–IFCC master equation: IFCC = (HbA1c − 2.152) ÷ 0.09148. 7% is 53 mmol/mol. This mmol/mol measures glycated hemoglobin, a different quantity from glucose in mmol/L.
HbA1c, average glucose and IFCC values
From the NGSP table, with 5.7% and 6.5% calculated by the same equations:
- 5.0%: 97 mg/dL (5.4 mmol/L), 31 mmol/mol
- 5.7%: 117 mg/dL (6.5 mmol/L), 39 mmol/mol, where prediabetes starts
- 6.0%: 126 mg/dL (7.0 mmol/L), 42 mmol/mol
- 6.5%: 140 mg/dL (7.8 mmol/L), 48 mmol/mol, where the diabetes range starts
- 7.0%: 154 mg/dL (8.6 mmol/L), 53 mmol/mol
- 8.0%: 183 mg/dL (10.2 mmol/L), 64 mmol/mol
- 9.0%: 212 mg/dL (11.8 mmol/L), 75 mmol/mol
- 10.0%: 240 mg/dL (13.4 mmol/L), 86 mmol/mol
ADA suggests below 7% as a goal for many non-pregnant adults with diabetes, adjusted to the individual.
How far to trust eAG
eAG is a population regression: in the 507-person ADAG study it explained 84% of the variation (R² = 0.84), so your measured average can sit well above or below it.
An average from occasional finger-stick readings is a weak input for the reverse conversion.
HbA1c itself can mislead in anemia, pregnancy, after blood loss or transfusion, and with some hemoglobin variants.
Three worked cases
- Default: 100 mg/dL converted to mmol/L, compared with the fasting cut-offs.
- HbA1c example: 7% converted to eAG in mg/dL.
- Inverse eAG example: an average of 126 mg/dL converted to HbA1c in %.
| Scenario | Mode result | Applicable category |
|---|---|---|
| Default | 5.55 | Prediabetes |
| HbA1c example | 154.20 | Diabetes range |
| Inverse eAG example | 6.02 | Prediabetes |
The first row is a trap: 5.55 mmol/L looks below the 5.6 mmol/L often quoted as the cut-off, yet it is exactly 100 mg/dL, where prediabetes starts. Near a boundary, compare unrounded values.
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Worked examples
7.0 mmol/L → mg/dL with factor 18
- Convert
- Glucose mmol/L → mg/dL
- Glucose
- 7.0 mmol/L
- mg/dL per mmol/L
- 18
- Result
- 126 mg/dL
- If this is a fasting reading (ADA)
- Diabetes range
Checked against: NGSP eAG table pairs 126 mg/dL with 7.0 mmol/L (factor 18); ADA fasting ≥ 126 mg/dL is diabetes range
7.0 mmol/L → mg/dL with factor 18.016
- Convert
- Glucose mmol/L → mg/dL
- Glucose
- 7.0 mmol/L
- Result
- 126.11 mg/dL
Checked against: 7.0 × 18.016 = 126.112
HbA1c 7% → eAG
- Convert
- HbA1c → estimated average glucose
- HbA1c
- 7%
- Result
- 154.2 mg/dL
- HbA1c (IFCC)
- 53 mmol/mol
- Estimated average glucose (mmol/L)
- 8.6 mmol/L
- HbA1c category (ADA)
- Diabetes range
Checked against: NGSP table: 7% ↔ 154 mg/dL, 8.6 mmol/L, 53 mmol/mol; ADAG 28.7 × 7 − 46.7 = 154.2
Questions
How do you convert mg/dL to mmol/L?
Divide by 18, or 18.016 exactly, from glucose's molar mass of 180.16 g/mol; to go from mmol/L to mg/dL, multiply. So 100 mg/dL is 5.55 mmol/L and 7.0 mmol/L is 126 mg/dL. The US mostly reports glucose in mg/dL, while the UK, Canada and Australia use mmol/L. The factor applies only to glucose; cholesterol and other substances have their own factors.
What is a normal blood sugar level?
For a fasting test, ADA classes below 100 mg/dL (5.6 mmol/L) as normal, 100–125 mg/dL (5.6–6.9 mmol/L) as prediabetes and 126 mg/dL (7.0 mmol/L) or more, confirmed by repeat testing, as diabetes. Two hours into a 75 g glucose tolerance test the cut-offs are 140 and 200 mg/dL (7.8 and 11.1 mmol/L). For people treated for diabetes, ADA calls a reading below 70 mg/dL (3.9 mmol/L) level 1 hypoglycaemia and below 54 mg/dL (3.0 mmol/L) level 2.
What does an HbA1c of 7 % mean?
It corresponds to an estimated average glucose of 154 mg/dL (8.6 mmol/L) over roughly the previous three months, by the ADAG equation 28.7 × 7 − 46.7, and to 53 mmol/mol in IFCC units. ADA's diagnostic threshold for diabetes is 6.5 % (48 mmol/mol), and below 7 % is the goal ADA suggests for many non-pregnant adults with diabetes, adjusted to the individual.
What HbA1c level is prediabetes?
From 5.7 % to below 6.5 % (39 to 47 mmol/mol) in the ADA criteria, with 6.5 % (48 mmol/mol) or higher, confirmed, in the diabetes range. By the ADAG equation, 5.7 % corresponds to an average glucose of 117 mg/dL (6.5 mmol/L) and 6.5 % to 140 mg/dL (7.8 mmol/L). HbA1c can mislead in anaemia, pregnancy, after blood loss or transfusion, and with some haemoglobin variants.
About this calculator
Sources
- Nathan DM et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31(8):1473–1478
- NGSP — HbA1c and estimated average glucose (eAG) table
- NGSP — IFCC standardization of HbA1c (master equation)
- American Diabetes Association. Standards of Care in Diabetes—2026, sections 2 (diagnosis, Tables 2.1 and 2.2) and 6 (glycemic goals and hypoglycemia). Diabetes Care 2026;49(Suppl 1)
For information only, not medical advice. These formulas describe populations, not you; talk to a clinician before acting on a result.
Checked against references
This calculator includes 7 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.