# What are my odds of having twins?

Shows the chance that a birth is twins for a mother of your age, and of your race and Hispanic origin, from the US twin birth rates for 2018 (NCHS), as a percent and as 1 in N.

- Page: https://www.acalculator.org/health/odds-of-twins-calculator
- JSON spec: https://www.acalculator.org/health/odds-of-twins-calculator.json
- Version: 8c4c49f4dae5

## Default answer

Example with the default inputs (Mother’s age at birth 32, Race and Hispanic origin Any): For a mother aged 32, about 3.62% of births are twins, about 1 in 28.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| age | Mother’s age at birth | The mother’s age in years when the baby is born. |
| group | Race and Hispanic origin | Optional: the mother’s race and Hispanic origin, for the rate of that group. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| chance | Chance of twins (by age) | Twin births per 1,000 births for mothers in this age group, as a percent. |
| oneIn | About 1 in | 1,000 ÷ the age group’s rate, rounded. |
| ageGroup | Age group | The NCHS age group used. |
| groupChance | Chance of twins (by race and Hispanic origin) | Twin births per 1,000 births for mothers of the chosen group, as a percent. |
| groupOneIn | About 1 in (by group) | 1,000 ÷ the group’s rate, rounded. |
| usChance | US average | Twin births per 1,000 births for all US mothers in 2018 (32.6), as a percent. |

## Method

Chance = twin births per 1,000 births for the age group (or race and Hispanic origin group) ÷ 10, in percent; 1 in N = 1,000 ÷ rate.

## Assumptions

- US births in 2018; the rates include twins conceived with fertility treatment.
- The age rate and the group rate are separate published rates; they are not combined.
- A rate for all births is not a personal prediction for one pregnancy.

## Worked examples

1. age = 32, group = any gives chance = 3.62%, oneIn = 28, ageGroup = 30 to 34, usChance = 3.26%. Source: Martin JA, Osterman MJK, NCHS Data Brief No. 351, Is Twin Childbearing on the Decline? United States, 2014–2018 (twin birth rates per 1,000 births, 2018), https://www.cdc.gov/nchs/products/databriefs/db351.htm (retrieved 2026-10-05).
2. age = 41, group = black gives chance = 5.11%, oneIn = 20, ageGroup = 40 and over, groupChance = 4.05%, groupOneIn = 25. Source: Martin JA, Osterman MJK, NCHS Data Brief No. 351, Is Twin Childbearing on the Decline? United States, 2014–2018 (twin birth rates per 1,000 births, 2018), https://www.cdc.gov/nchs/products/databriefs/db351.htm (retrieved 2026-10-05).
3. age = 19, group = hispanic gives chance = 1.71%, oneIn = 58, ageGroup = under 20, groupChance = 2.44%, groupOneIn = 41. Source: Martin JA, Osterman MJK, NCHS Data Brief No. 351, Is Twin Childbearing on the Decline? United States, 2014–2018 (twin birth rates per 1,000 births, 2018), https://www.cdc.gov/nchs/products/databriefs/db351.htm (retrieved 2026-10-05).

## FAQ

### What are the odds of having twins?

In the United States in 2018, 32.6 of every 1,000 births were twins, about 3.3%, or 1 in 31. The chance is higher for older mothers and differs by race and Hispanic origin.

### Does the mother’s age change the odds of twins?

Yes. In 2018 the twin rate rose from 17.1 per 1,000 births for mothers under 20 to 51.1 per 1,000 for mothers 40 and over.

### Do twins run in families?

The published US rates are not split by family history, so this page cannot add it. Ask your doctor how your own history changes your chances.

### Do the rates include fertility treatment?

Yes. They count all US births in 2018, including births after fertility treatment, so they are not rates for natural conception only.

### Why do the age and race results differ?

They are two separate published rates: one for all mothers of an age group, and one for all mothers of a race and Hispanic origin group. The page shows both and does not combine them, because the source gives no combined table.

### Is the twin rate going down?

The US twin birth rate fell from 33.9 per 1,000 births in 2014 to 32.6 in 2018 (NCHS Data Brief 351).

## Sources

- Martin JA, Osterman MJK. Is Twin Childbearing on the Decline? United States, 2014–2018. NCHS Data Brief No. 351. National Center for Health Statistics, 2019, retrieved 2026-10-05. https://www.cdc.gov/nchs/products/databriefs/db351.htm