Online Tool Store
Insulin Sensitivity Factor Calculator
Calculate your Insulin Sensitivity Factor from total daily dose using the 1800/1500 rules, then estimate the correction bolus needed to reach a target blood glucose.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Sum of all basal (long-acting) and bolus (mealtime) units per 24 hours.
Insulin Sensitivity Factor (ISF)
Recommended Correction Bolus
Calculation Steps & Ratios
| Metric | Value | Clinical Formula |
|---|
How it works
- Enter your Total Daily Dose (TDD) of insulin (the combined total of all basal long-acting and mealtime bolus units).
- Select the insulin type to apply the corresponding clinical formula (1800 Rule for rapid-acting or 1500 Rule for regular insulin).
- Input your current blood glucose reading and your physician-recommended target blood glucose.
- The calculator determines your Insulin Sensitivity Factor and the appropriate corrective bolus dosage.
The formula
ISF (mg/dL per Unit) = 1800 / Total Daily Dose (TDD)
Correction Bolus (Units) = (Current BG − Target BG) / ISF
FAQ
What is an Insulin Sensitivity Factor (ISF)?
The Insulin Sensitivity Factor (also known as a Correction Factor) indicates how many milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L) one unit of rapid-acting insulin is expected to lower your blood glucose level.
What is the 1800 Rule vs the 1500 Rule?
The 1800 Rule is typically used for modern rapid-acting insulin analogs (such as lispro, aspart, and glulisine). The 1500 Rule is applied when using older regular short-acting human insulin.
How is a correction bolus dose calculated?
A correction bolus is determined by subtracting your target blood glucose from your current blood glucose level, then dividing that difference by your personalized Insulin Sensitivity Factor: Correction Dose = (Current BG − Target BG) / ISF.
Does this calculator account for Insulin-on-Board (active insulin)?
No. This tool computes raw correction requirements based on static glucose readings. In clinical practice, you must also factor in active insulin remaining from recent boluses ("insulin-on-board" or IOB) to avoid insulin stacking and hypoglycemia.
How we compare
| Feature | Online Tool Store | Diabetes pump algorithms | Paper logs |
|---|---|---|---|
| Multi-formula support (1500, 1800, 2000 rules) | ✓ | Fixed config | ✗ |
| Instant mg/dL and mmol/L equivalents | ✓ | ✓ | ✗ |
| Free & private (no data uploaded) | ✓ | Cloud account required | ✓ |