# Blood Donor Compatibility Calculator

URL: https://speedycalculator.com/calculators/health/blood-donor/
Last updated: 2026-10-30

> The blood donor compatibility calculator shows which blood types you can give red cells, plasma and platelets to, and receive them from, based on your ABO and Rh blood group.

## Inputs

- ABO group
- Rh type

## Results

- You can give red cells to
- You can receive red cells from
- You can give plasma to
- You can receive plasma from

## Formula

```
Red cells: O− is the universal donor, AB+ the universal recipient
Plasma: AB is the universal plasma donor, O the universal plasma recipient
```

## Explanation

Antibodies in the recipient's plasma attack red cells with antigens they lack, so red cell compatibility follows the recipient's antibodies. For plasma it is the reverse. Rh-negative people should receive Rh-negative red cells, especially girls and women who may become pregnant.

### How to use the Blood Donor Compatibility Calculator

- **ABO group**
- **Rh type**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Choose your ABO group and Rh type.

### Inputs explained

FieldWhat to enterABO groupChoose one: A, B, AB, ORh typeChoose one: Rh positive, Rh negative

### What each result means

- **You can give red cells to** = ([ABO group] - 1)×2 + [Rh type] - 1
- **You can receive red cells from** = ([ABO group] - 1)×2 + [Rh type] - 1
- **You can give plasma to** = [ABO group] - 1
- **You can receive plasma from** = [ABO group] - 1

*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — ABO group: O; Rh type: Rh positive.

Results — **You can give red cells to = All Rh-positive types**; You can receive red cells from = O+, O−; You can give plasma to = O only; You can receive plasma from = Everyone.

## Key terms

- **ABO**: Blood group system with A, B, AB and O types.
- **Rh**: Rhesus D antigen (positive or negative).

## FAQ

**What is the universal donor?**
O negative for red cells; AB for plasma.

**What is the rarest blood type?**
AB negative in most populations.

**Why is O negative in such demand?**
It can be given in emergencies before a patient's group is known.


## Sources

- [American Red Cross – Blood types](https://www.redcrossblood.org/donate-blood/blood-types.html)