Carbohydrate Ratio
Apply the 500 rule to total daily insulin dose (TDD) to estimate a starting grams-of-carbohydrate-per-unit ratio.
How to use
- Enter total daily insulin dose in units/day.
- Calculate the starting estimate 500÷TDD.
Capabilities and scope
The only input is TDD, not a meal carbohydrate amount; output is shown as 1 unit : x g.
How it works
estimatedGramsPerUnit=500/TDD.
Example
TDD 40 units/day gives about 1 unit : 12.5 g.
Interpretation
TDD must be greater than zero and no more than 300.
Useful for
- Inspect the mathematics of the 500-rule starting estimate
- Understand how the ratio changes with TDD
Before you use it
- Actual ratios vary by person, time of day, activity, and other factors; do not change insulin dosing from this result alone.
Edge cases
- Do not use this calculator alone for medication dosing decisions.
Standards and references
Frequently asked questions
Can I dose insulin directly from this result?
No. The runner explicitly presents it as a starting estimate; dosing changes require guidance from the diabetes care team.