Time in Range (TIR) Calculator
Time in Range (TIR) Calculator
Turn a CGM time-in-range percentage into hours and minutes a day and check it against the 2019 international consensus target for the right population — because the pregnancy target is 70% of a completely different glucose range, and reading one against the other is the error this page exists to prevent.
Time in range
Population + percentages → hours in rangeType 1 diabetes, time in range 62%, time below range 5%, below 3.0 mmol/L 1.4%, above range 33%, CV 41%
Formula and the consensus targets
- type 1 or type 2 diabetes
- TIR > 70% (> 16 h 48 min) at 3.9–10.0 mmol/L; time below 3.9 < 4% (< 1 h) of which below 3.0 < 1% (< 15 min); time above 10.0 < 25% (< 6 h) of which above 13.9 < 5% (< 1 h 12 min)
- older or high-risk
- TIR > 50% (> 12 h) at 3.9–10.0 mmol/L; time below 3.9 < 1% (< 15 min); time above 13.9 < 10% (< 2 h 24 min). Lower time-in-range bar, much tighter hypoglycaemia limit
- pregnancy with type 1 diabetes
- TIR > 70% (> 16 h 48 min) at 3.5–7.8 mmol/L (63–140 mg/dL); time below 3.5 < 4% (< 1 h) of which below 3.0 < 1% (< 15 min); time above 7.8 < 25% (< 6 h). The range itself is different, not just the percentage
- glycaemic variability
- coefficient of variation ≤ 36%. The accepted consensus draft notes that some authors suggest ≤ 33% for additional protection against hypoglycaemia
- how much data
- 14 days of CGM wear with at least 70% data capture. Fewer days or a sparser record makes the percentages unstable, and the consensus does not support reading them as targets
- type 2 in pregnancy, and gestational diabetes
- the consensus gives no numeric targets for these. It points to the pregnancy narrative and says more research is needed. Borrowing the type 1 pregnancy row for them is not supported
Worked example
Type 1 diabetes, time in range 62%, time below range 5%, below 3.0 mmol/L 1.4%, above range 33%, CV 41%
62 × 24 ÷ 100 = 14.88 hours, which is 14 h 53 min in range
The target is more than 70% — 16.8 hours, or 16 h 48 min — so this profile is about 1 h 55 min short
But the time in range is not the number to act on first
1.4% below 3.0 mmol/L is 20 minutes a day of level 2 hypoglycaemia, above the 1% (15 min) limit
5% below range is 1 h 12 min, above the 4% (1 h) limit
A CV of 41% is above the 36% target, which is the same finding stated another way: the lows are driving the variability
So the useful move is to reduce the hypoglycaemia. Time in range usually rises as a consequence, because the rebound highs that follow the lows disappear with them
The 2019 international consensus targets
| Type 1 / type 2 | Older or high-risk | Pregnancy, type 1 | |
|---|---|---|---|
| Target range | 3.9–10.0 mmol/L (70–180 mg/dL) | 3.9–10.0 mmol/L (70–180 mg/dL) | 3.5–7.8 mmol/L (63–140 mg/dL) |
| Time in range | > 70% (> 16 h 48 min) | > 50% (> 12 h) | > 70% (> 16 h 48 min) |
| Below the range, total | < 4% (< 1 h) | < 1% (< 15 min) | < 4% (< 1 h) |
| Below 3.0 mmol/L (54 mg/dL) | < 1% (< 15 min) | included in the above | < 1% (< 15 min) |
| Above the range, total | < 25% (< 6 h) | not separately specified | < 25% (< 6 h) |
| Above 13.9 mmol/L (250 mg/dL) | < 5% (< 1 h 12 min) | < 10% (< 2 h 24 min) | not separately specified |
| Coefficient of variation | ≤ 36% | ≤ 36% | ≤ 36% |
Percentage to time per day
| % of readings | Time per day | Where this figure appears |
|---|---|---|
| 1% | 14 min 24 s | Limit for time below 3.0 mmol/L in every population, and for total time below range in the older/high-risk group |
| 4% | 57 min 36 s | Limit for total time below range — general and pregnancy |
| 5% | 1 h 12 min | Limit for time above 13.9 mmol/L — general |
| 10% | 2 h 24 min | Limit for time above 13.9 mmol/L — older/high-risk |
| 25% | 6 h | Limit for total time above range |
| 50% | 12 h | Time-in-range target — older/high-risk |
| 70% | 16 h 48 min | Time-in-range target — general and pregnancy |
| 100% | 24 h |
Time in range is not GMI, and neither is HbA1c
| Metric | What it is | What it cannot tell you |
|---|---|---|
| Time in range | The proportion of sensor readings inside a stated glucose range over the wear period | Nothing about where the rest of the readings went. 70% in range with 10% below 3.0 mmol/L and 70% in range with all the remainder high are the same number and different clinical problems |
| Glucose management indicator | A single figure computed from the MEAN sensor glucose by regression against laboratory HbA1c | Nothing about distribution at all. Two people with identical GMI can have completely different times in range, because a mean is indifferent to how it was reached |
| Laboratory HbA1c | Glycation of haemoglobin over the red cell lifespan, roughly 90 to 120 days | Nothing about variability, and it is distorted by anaemia, haemoglobinopathy, chronic kidney disease, recent transfusion and pregnancy — none of which touch a CGM metric |
Which population, and why the pregnancy row is different
Time in range comes from the 2019 international consensus, which set out to give continuous glucose monitoring data a small number of metrics that could be reported consistently and compared between clinics. The headline metric is the proportion of sensor readings falling between 3.9 and 10.0 mmol/L (70 to 180 mg/dL), and the target for most people with type 1 or type 2 diabetes is more than 70% of the day — which the consensus itself expresses as more than 16 hours and 48 minutes, because a percentage of a day is far easier to act on when it is stated as a time. Roughly speaking, each 10 percentage points of time in range corresponds to about half a percentage point of HbA1c, which is the reason the metric caught on.
There are three rows in that consensus table, not one, and choosing the wrong one is the mistake this page is built to prevent. For an older or high-risk person the time-in-range target drops to more than 50% — 12 hours — while the hypoglycaemia limit tightens fourfold, from under 4% to under 1% of the day below 3.9 mmol/L. That is a deliberate trade: in someone for whom a fall or a hospital admission is the dominant risk, less time low is worth more than more time in range. And for pregnancy in type 1 diabetes the target percentage stays at 70% but the range it is measured over changes, to 3.5 to 7.8 mmol/L (63 to 140 mg/dL). Those two numbers, 70% and 70%, describe entirely different amounts of glycaemic control, and a pregnancy time in range cannot be compared with a pre-pregnancy one. Women commonly see their reported time in range fall at conception even though nothing has worsened, because the measuring stick got shorter.
Two limits sit underneath all of this. First, the numbers only mean something on enough data: 14 days of wear with at least 70% data capture is the minimum the consensus supports, and percentages from three days of a sensor that kept losing signal are not a target, they are noise. Second, time in range is a single summary of a distribution and it hides the tails on purpose. A profile with 70% in range and 5% of the day below 3.0 mmol/L meets the headline target and is dangerous. The consensus therefore publishes five numbers rather than one, and they are read in a fixed order: level 2 hypoglycaemia first, then total time below range, then time in range, then the two above-range figures. Raising time in range by letting glucose run higher is not an improvement, and raising it by tolerating more lows is worse than no change at all.
Finally, time in range and the glucose management indicator are different things and the difference is not subtle. GMI is computed from the mean sensor glucose alone, by the regression Bergenstal and colleagues fitted against laboratory HbA1c. A mean is indifferent to how it was reached, so two people with the same GMI can have wildly different times in range — one steady around 8 mmol/L, the other oscillating between 3 and 16. Time in range and the coefficient of variation describe the shape of the distribution; GMI and HbA1c describe its centre. Use both, know which is which, and if the two disagree, believe the distribution.
Frequently asked questions
What is a good time in range?
More than 70% of the day — 16 hours 48 minutes — between 3.9 and 10.0 mmol/L (70 to 180 mg/dL) for most people with type 1 or type 2 diabetes. More than 50% (12 hours) for an older or high-risk person. In pregnancy with type 1 diabetes the target is again more than 70%, but of a narrower range, 3.5 to 7.8 mmol/L.
Why is the pregnancy target different?
Because the range itself changes, not just the percentage. The pregnancy target range is 3.5 to 7.8 mmol/L (63 to 140 mg/dL) against 3.9 to 10.0 outside pregnancy. Both ask for more than 70%, so the two figures look comparable and are not — a pregnancy time in range is a percentage of a much narrower band.
How much CGM data do I need for time in range to mean anything?
At least 14 days of wear with at least 70% data capture, per the same consensus that set the targets. Fewer days, or a sensor that kept dropping out, gives percentages that move substantially with the next day’s data.
How do I convert time in range from a percentage to hours?
Multiply the percentage by 0.24 to get hours, or by 14.4 to get minutes. So 70% is 16.8 hours, or 16 h 48 min; 4% is about 58 minutes; 1% is about 14 minutes. The consensus prints both columns because a percentage understates how much time is involved.
Is time in range the same as GMI?
No. GMI is calculated from the mean sensor glucose alone and says nothing about distribution; time in range describes the distribution and says nothing about the mean. Two people with the same GMI can have very different times in range, and a person can improve time in range without moving GMI much at all.
My time in range is above 70% but I get lows. Is that fine?
No. The consensus sets four other limits alongside the 70%, and the hypoglycaemia ones come first: under 4% of the day below the lower limit and under 1% — about 15 minutes — below 3.0 mmol/L (54 mg/dL). A time in range above target with level 2 hypoglycaemia present is not a profile at target.
Are there time-in-range targets for gestational diabetes?
Not numeric ones in the 2019 consensus, which gives targets for pregnancy in type 1 diabetes and states that more research is needed for type 2 diabetes and gestational diabetes in pregnancy. Using the type 1 pregnancy row for them is not supported by the document.
Related calculators
References
- Battelino T, Danne T, Bergenstal RM, et al. Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range. Diabetes Care. 2019;42(8):1593–1603.
- Battelino T, Alexander CM, Amiel SA, et al. Continuous glucose monitoring and metrics for clinical trials: an international consensus statement. Lancet Diabetes Endocrinol. 2023;11(1):42–57.
- Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI): A New Term for Estimating A1C From Continuous Glucose Monitoring. Diabetes Care. 2018;41(11):2275–2280.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.