Carb/Insulin Ratio (ICR) and Insulin Sensitivity Factor (ISF)
Computes ICR (rule of 500/450) and ISF (rule of 1800/1500) from your Total Daily Dose (TDD). Estimates meal bolus and correction from carbs, current BG and target.
Notice: educational tool, based on the 500/450 and 1800/1500 rules. Always confirm ICR and ISF with an endocrinologist — they vary by person, time of day and activity.
Insulin-to-carb ratio (ICR) and sensitivity factor (ISF)
If you're on intensive insulin therapy, two personal numbers do most of the work at mealtimes and when you correct a high reading. The insulin-to-carb ratio (ICR) tells you how many grams of carbohydrate one unit of insulin will cover. The insulin sensitivity factor (ISF), sometimes called the correction factor, tells you how many mg/dL one unit drops your blood glucose. People usually estimate both from their total daily dose (TDD), the sum of all the basal plus bolus insulin used on a typical day, with a few simple rules taught in diabetes education.
How it works
With rapid-acting analog insulin (lispro, aspart, glulisine), the 500 rule gives ICR = 500 / TDD and the 1800 rule gives ISF = 1800 / TDD. Regular human insulin acts more slowly, so it uses the 450 rule (ICR = 450 / TDD) and the 1500 rule (ISF = 1500 / TDD). With those in hand, a meal bolus comes out to carbs / ICR and a correction bolus to (current glucose − target glucose) / ISF. Treat the formulas as rough starting points. They fit people on a basal/bolus regimen best, and you tighten them over time using your own glucose data.
Worked example
Take a TDD of 50 units of rapid-acting analog. That gives ICR = 500 / 50 = 10 g per unit and ISF = 1800 / 50 = 36 mg/dL per unit. A 60 g meal needs 60 / 10 = 6 units. Say the current glucose reads 200 mg/dL against a target of 110; the correction works out to (200 − 110) / 36 ≈ 2.5 units. Add them up and you land near 6 + 2.5 = 8.5 units, before whatever rounding your clinician advises.
FAQ
Why two different rules? Each unit of a rapid analog acts faster and harder, which is why they use the larger numerators (500/1800). Regular insulin is slower, and the smaller numerators (450/1500) match its weaker per-unit effect.
Can my ICR and ISF change during the day? They can. Lots of people are more insulin-resistant at breakfast and need a tighter morning ICR. Exercise, illness, stress, hormones, all of it shifts these numbers.
Medical disclaimer: This tool is meant for education and is not a substitute for advice from an endocrinologist or your diabetes care team. The 500/450 and 1800/1500 rules only give rough estimates. Real insulin doses have to be individualized, prescribed and supervised by a qualified healthcare professional working from your own glucose data. Never start or change insulin dosing on the strength of this calculator alone.
Related Tools
Clinker Lime Saturation Factor (LSF)
Computes the lime saturation factor of raw meal or clinker, the index that tells how close the lime present sits to the maximum that silica, alumina and iron oxide could combine with: LSF = 100 × CaO ÷ (2.8 × SiO₂ + 1.18 × Al₂O₃ + 0.65 × Fe₂O₃), with contents as mass percentages. It is the number one parameter in cement kiln control because it governs the split between alite and belite: a value near 100 means nearly all the lime combines and the clinker comes out rich in C₃S, with good early strength, but it demands a hotter burn and a narrow operating margin. Above 100 free lime is left over, hydrating late and expanding in concrete; below 90 the clinker is poor in alite and 3-day strength drops. The form without free lime correction was adopted, as used in raw meal control; on burnt clinker some laboratories subtract free CaO from the numerator, which lowers the index by one or two points. Enter the CaO, SiO₂, Al₂O₃ and Fe₂O₃ contents of the sample.
Fabric Cover Factor
Compute a fabric's cover factor, CF = thread density (threads/cm) · √(Tex), an index of how 'closed' the weave is — how much the threads cover the area, leaving more or fewer open spaces. High factors indicate dense, opaque fabrics (canvas, twill); low ones, sheer, breathable fabrics (voile, mesh). It influences air permeability, opacity and strength. Enter the thread density and the count in Tex.
Film ISO Light Speed Relation
Calculates equivalent shutter speed when changing film ISO.
TDEE from BMR and Activity Factor
Multiplies basal metabolic rate in kcal by an activity factor between 1.2 (sedentary) and 1.9 (athlete) to give total daily energy expenditure in kcal per day.
RLC Quality Factor Q Calculator
Computes the quality factor Q of a series RLC circuit from R, L and C using the ratio between reactance and resistance.
Load Factor Bank Angle Calculator
Computes load factor (g) in level turn from bank angle in degrees as the aircraft maintains altitude during typical maneuver or training.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.