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Blood Donation Time Calculator

Find your next eligible donation date by donation type, using either the American Red Cross or the French EFS intervals.

Related tools

All Medical & clinical tools →
Blood Pressure Category CalculatorClassify a reading with the ACC/AHA 2017 or the European ESC/ESH scale, plotted on a chart, with mean arterial pressure and pulse pressure.Blood Sugar Converter (mg/dL ↔ mmol/L)Convert blood glucose between mg/dL and mmol/L in both directions, and see where the value falls against the ADA reference bands.Blood Type CalculatorPredict a child's possible ABO and Rh blood types, with probabilities, from both parents' blood groups.Blood alcohol calculatorEstimate your blood alcohol concentration (BAC) with the Widmark formula.hCG Doubling Time CalculatorCompute the doubling time and percentage rise between two hCG results, read against the expected range for the level reached.HbA1c Calculator (A1c ↔ eAG)Enter HbA1c, average glucose in mg/dL or in mmol/L and get the other two, plus the IFCC value in mmol/mol.Heart Disease Risk CalculatorEstimate your 10-year risk of heart attack and stroke with the 2013 ACC/AHA Pooled Cohort Equations (ASCVD), from age, sex, cholesterol, blood pressure and risk factors.Insulin Sensitivity Factor CalculatorEstimate 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.

Open Blood Donation Time Calculator and you get an answer straight away, with no account to create. It sits under Medical & clinical in our catalogue, alongside Blood Pressure Category Calculator and Blood Sugar Converter (mg/dL ↔ mmol/L).

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 is Blood Donation Time Calculator?

Find your next eligible donation date by donation type, using either the American Red Cross or the French EFS intervals.

When would I actually use this?

Checking one clinical number against the definition that gives it meaning: a dose against a body weight, a laboratory value corrected for the albumin or glucose that distorted it, a blood pressure against a guideline's threshold table, a heart rate or a basal metabolic rate against the formula that defines it.

What is the most common mistake?

Reading the output as a finding. Every figure here is arithmetic on numbers you typed: a correction formula measures nothing, and a threshold table classifies one reading rather than a person. Blood pressure in particular means little until it has been measured repeatedly on separate occasions, and a dose worked out here is a way of checking a prescription, never of writing one.

How is Blood Donation Time Calculator different from Blood Pressure Category Calculator?

They sit next to each other but answer different questions: Blood Pressure Category Calculator is the one to open when you need it to classify a reading with the ACC/AHA 2017 or the European ESC/ESH scale, plotted on a chart, with mean arterial pressure and pulse pressure. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Blood Sugar Converter (mg/dL ↔ mmol/L) is the closest one after this: Convert blood glucose between mg/dL and mmol/L in both directions, and see where the value falls against the ADA reference bands.

What else is worth having open alongside it?

Blood Type Calculator and Blood alcohol calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Each tool names the published formula it applies, on its own page: the Payne correction for calcium, Katz (1.6) and Hillier (2.4) for glucose-corrected sodium, Mifflin-St Jeor for basal metabolic rate, Widmark for blood alcohol, 220 − age for maximum heart rate, the 2013 ACC/AHA Pooled Cohort Equations for cardiovascular risk, and five published formulas side by side for body surface area. The classification tools use the guideline tables themselves — ACC/AHA 2017, ESC/ESH and ESC 2024 for blood pressure, the ADA Standards of Care for glucose — and where guidelines disagree the tool shows the reading under each rather than picking one. None of this is a diagnosis, and none of it knows the history, medication or comorbidity that decides what a number means.

Further reading

All guides →
ExplainerBlood Donation Intervals, and What Your Body Is Actually ReplacingPlasma is back in a day, red cells in weeks, iron in months — and it is the iron that sets the interval. The arithmetic of a unit, and the minimum intervals published by seven national services.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.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.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.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.