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Insulin To Carb Ratio Calculator

Work out insulin to carb ratio instantly with clear inputs, formula shown and shareable results.

About Insulin To Carb Ratio Calculator

Uses the 500 rule (or 450 for regular insulin) to estimate how many grams of carbohydrate one unit of mealtime insulin covers.

Formula

Carbohydrate ratio

Grams per unit = constant / total daily dose; units for a meal = carbohydrate grams / ratio

Worked example

With the default values below, Insulin To Carb Ratio Calculator returns Grams of carbohydrate covered per unit of 10.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total daily insulin doseaccepts 5–300 units
50 units
Rule constantone of 500 rule (rapid-acting analogue), 450 rule (regular insulin)
500 rule (rapid-acting analogue)

Results

Grams of carbohydrate covered per unit
10.0 g/unit
Units needed for 50 g of carbohydrate
5.00 units
Rule constant
500

Step by step

  1. 1Values used
  2. 2Carbohydrate ratio
  3. 3Grams of carbohydrate covered per unit= 10.0 g/unit
  4. 4Units needed for 50 g of carbohydrate= 5.00 units
  5. 5Rule constant= 500

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why 500?

It is an empirical constant derived from population data relating total daily dose to carbohydrate handling.

Should every meal use the same ratio?

Not necessarily; many people need a tighter ratio at breakfast than later in the day.

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