Time in Range (TIR) Calculator
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — September 2026
Work out your time in range, time below range and time above range from your CGM readings — the core glucose metrics behind modern diabetes targets.
Below 70 mg/dL (3.9 mmol/L).
70–180 mg/dL (3.9–10.0 mmol/L) (3.9–10.0 mmol/L).
Above 180 mg/dL (10.0 mmol/L).
Two people can both have an A1c of 7.0% and be having completely different experiences of diabetes. One may sit steadily between 5 and 9 mmol/L. The other may be swinging between hypoglycemia and 15, averaging out to the same figure. A single number cannot distinguish them — and the difference matters enormously, both for how you feel and for long-term risk.
Time in range describes what A1c cannot: the proportion of the day spent inside target, above it and below it. It is now the primary CGM metric in international consensus guidance, with A1c increasingly treated as a supporting figure rather than the headline.
The standard targets are more than 70% of the day in range, less than 4% below 3.9 mmol/L, and less than 1% below 3.0. That hypoglycemia limit is the one that most deserves attention: it is a much tighter constraint than most people realise, and improving time in range by pushing glucose down without watching time below range simply trades one problem for a more dangerous one.
Enter your readings below. Beneath the calculator you will find how each figure is derived, the full consensus targets by group, and practical ways to shift the numbers.
How to Use This Calculator
- Enter your number of readings below range (under 70 mg/dL; 3.9 mmol/L).
- Enter readings in range (70–180 mg/dL; 3.9–10.0 mmol/L) and above range (over 180).
- Calculate to see your TIR, time below range and time above range as percentages, with how they compare to target.
You can pull these counts from a CGM report, or estimate them from finger-stick logs. Because each CGM reading is an equal slice of time, counting readings gives the same percentages as time.
How Time in Range Is Calculated
Time in range is the percentage of your CGM readings (or time) that fall within the target glucose band, usually 70–180 mg/dL (3.9–10.0 mmol/L). Because each CGM reading represents an equal slice of time, counting readings in each band gives the same percentages as time:
Example: 560 in-range of 800 total → 560 ÷ 800 × 100 = 70% TIR.
Standard CGM Targets (Type 1 & Type 2)
| Metric | Range | Goal |
|---|---|---|
| Time in range (TIR) | 70–180 mg/dL (3.9–10.0 mmol/L) | > 70% |
| Time below range (TBR) | < 70 mg/dL (3.9 mmol/L) | < 4% |
| Time very below range | < 54 mg/dL (3.0 mmol/L) | < 1% |
| Time above range (TAR) | > 180 mg/dL (10.0 mmol/L) | < 25% |
Pregnancy and other groups use tighter or different targets — confirm yours with your team.
How to Improve Your Time in Range
Reducing time above range (highs)
The biggest gains usually come from meals: pre-bolusing rapid insulin ~15 minutes before eating, counting carbs more accurately, and a short walk after meals all blunt post-meal spikes. Persistent highs may need a basal, carb-ratio or correction-factor change — make those with your care team.
Reducing time below range (lows)
Safety comes first. Treat lows with the rule of 15 (about 15 g fast-acting carbs, recheck in 15 minutes) and avoid over-treating, which causes a rebound high. Recurrent lows often mean too much basal or correction, or unaccounted-for exercise or alcohol — review the pattern rather than just reacting to single readings.
Frequently Asked Questions
What is a good time in range?
For most adults with type 1 or type 2 diabetes, the goal is more than 70% of time in the 70–180 mg/dL range, with less than 4% below 70 mg/dL. Higher TIR generally corresponds to a lower A1c.
How does time in range relate to A1c?
They move together: roughly, about 70% time in range corresponds to an A1c near 7%. But TIR also shows variability and hypoglycemia that a single A1c cannot, which is why both are useful.
How much does each 5% of time in range matter?
An increase of about 5% in time in range (roughly 1.2 hours per day) is considered a clinically meaningful improvement. Small, sustained gains add up over time.
Should I focus on time in range or time below range first?
Safety first: reducing time below range (hypoglycemia) is usually the priority, then improving time in range. Discuss any changes to insulin or targets with your care team.
What is the time in range target in pregnancy?
Pregnancy uses a tighter range. For type 1 diabetes in pregnancy the target band is 63–140 mg/dL (3.5–7.8 mmol/L), with a goal of more than 70% time in range, under 4% below 63 mg/dL, and under 1% below 54 mg/dL. Your obstetric and diabetes teams set your individual goals.
Does time in range replace A1c?
It complements rather than fully replaces A1c. Time in range adds what A1c can't show — day-to-day variability and how much time is spent low — while A1c remains a validated long-term marker tied to complication risk. Most care teams now look at both together.
Sources
- Battelino T, et al. Clinical targets for CGM data interpretation: international consensus on time in range. Diabetes Care. 2019. Link
- American Diabetes Association. Standards of Care — glycemic targets and CGM. Link
Written by Ryan Mitchell · Last updated: September 2026