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Insulin Sensitivity Factor Calculator

Estimate your correction factor from the total daily dose with the 1500/1700/1800/2000 rule, in mg/dL or mmol/L, plus an optional correction dose.

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Open Insulin Sensitivity Factor Calculator and you get an answer straight away, with no account to create. It sits under Medical & clinical in our catalogue, alongside Carb-to-Insulin Ratio Calculator and Blood Donation Time Calculator.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Insulin Sensitivity Factor Calculator do?

Estimate your correction factor from the total daily dose with the 1500/1700/1800/2000 rule, in mg/dL or mmol/L, plus an optional correction dose.

When would I actually use this?

Checking a starting point for a correction factor — how far one unit is expected to move blood glucose — against the rule of thumb, or sanity-checking the factor already programmed on a pump.

What is the most common mistake?

Correcting on top of a dose that is still working. The factor says nothing about insulin on board, and stacking corrections is the classic route to a hypo. Sensitivity also changes with exercise, illness and time of day, so a single number is a starting estimate a clinical team adjusts, not a setting.

How is Insulin Sensitivity Factor Calculator different from Carb-to-Insulin Ratio Calculator?

They sit next to each other but answer different questions: Carb-to-Insulin Ratio Calculator is the one to open when you need it to estimate a starting carb ratio from your total daily dose using the 400/450/500/550 rule, with an optional mealtime bolus. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Blood Donation Time Calculator is the closest one after this: Find your next eligible donation date by donation type, using either the American Red Cross or the French EFS intervals.

What else is worth having open alongside it?

Blood Pressure Category Calculator and Blood Sugar Converter (mg/dL ↔ mmol/L) — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

The 1800 rule, from the same body of structured diabetes education as the carbohydrate ratio: correction factor in mg/dL per unit = 1800 ÷ total daily dose. The tool shows which constant it used — 1500 for regular human insulin, 1700 and 2000 as variants by sensitivity — and divides the constant by 18.016 first when the answer is asked for in mmol/L. A rule of thumb for a starting point, adjusted in practice against what actually happens.

Further reading

All guides →
ExplainerThe Insulin Sensitivity Factor and the 1800 RuleThe correction factor says how far one unit of insulin moves glucose, and the classical estimate is 1800 divided by the total daily dose in mg/dL — or 100 divided by it in mmol/L. Those are the same rule, and here is the arithmetic that proves it, plus why stacking is the error that actually hurts.ExplainerHbA1c to Average Blood Sugar: The Full Conversion TableAn HbA1c of 7 percent corresponds to an average glucose of about 154 mg/dL, or 8.5 mmol/L, or 53 mmol/mol. Here is the whole table, the formulas behind it, and when the number cannot be trusted.ExplainerBlood Sugar Units: mg/dL, mmol/L, and Why Both ExistThe conversion factor is not 18 — it is 18.016, and it is the molar mass of glucose divided by ten. Here is where it comes from, which countries use which unit, and every diagnostic threshold in both scales with the guideline it belongs to.ExplainerThe Carbohydrate-to-Insulin Ratio, and the Rule That Estimates ItThe ratio says how many grams of carbohydrate one unit of insulin covers, and the usual starting estimate is 500 divided by the total daily dose. Here is where that number comes from, how sharply it moves across daily doses, why a 450 version exists, and the three things it quietly assumes.ExplainerHow Heart Disease Risk Scores Work — and Why They Disagree About YouFramingham, SCORE2 and the pooled cohort equations use overlapping but different inputs and were calibrated on different populations, so the same person gets three different percentages. Here is what each one asks for and what the number means.ExplainerHow Blood Type Is Inherited: The Full Parent-to-Child TableEach parent passes on one ABO allele — A, B or O — and Rh follows a separate gene. Here is every parent combination, which child types it can and cannot produce, and why this is not a paternity test.