Long and Wide Data Format Converter

Created:December 17, 2024

Last Updated:March 22, 2025

Tool

1. Upload Your Data

Not sure about data formats? Check out the examples in the Learn More section below. Save your data when you are done because this tool does not save your data anywhere.

Learn More

Understanding Long and Wide Data Formats

Long Format (Tidy)

Each row is an observation, with variables in columns

ID,Year,Measurement,Value
1,2020,Temperature,18.5
1,2020,Humidity,30
1,2021,Temperature,19.0
1,2021,Humidity,32
2,2020,Temperature,17.0
2,2020,Humidity,40
2,2021,Temperature,16.5
2,2021,Humidity,42

Wide Format

Data spread across multiple columns with unique identifiers

ID,Year,Temperature,Humidity
1,2020,18.5,30
1,2021,19.0,32
2,2020,17.0,40
2,2021,16.5,42

Long to Wide Transformation

Original Data (Long Format)

ID	Year	Measurement	Value
1	2020	Temperature	18.5
1	2020	Humidity	30
1	2021	Temperature	19
1	2021	Humidity	32
2	2020	Temperature	17
2	2020	Humidity	40
2	2021	Temperature	16.5
2	2021	Humidity	42

Column Selection for Long to Wide

Select these columns:

ID Columns:

ID (identifies unique entries)
Year (identifies unique entries)

Value Columns:

Measurement (will become new column names)
Value (will fill the new columns)

Result (Wide Format)

ID	Year	Temperature	Humidity
1	2020	18.5	30
1	2021	19	32
2	2020	17	40
2	2021	16.5	42

Wide to Long Transformation

Original Data (Wide Format)

ID	Year	Temperature	Humidity
1	2020	18.5	30
1	2021	19	32
2	2020	17	40
2	2021	16.5	42

Column Selection for Wide to Long

Select these columns:

ID Columns:

ID (stays as is)
Year (stays as is)

Value Columns:

Temperature (will be stacked)
Humidity (will be stacked)

This will create two new columns: "Measurement" (containing "Temperature" or "Humidity") and "Value" (containing the corresponding numbers)

Result (Long Format)

ID	Year	Measurement	Value
1	2020	Temperature	18.5
1	2020	Humidity	30
1	2021	Temperature	19
1	2021	Humidity	32
2	2020	Temperature	17
2	2020	Humidity	40
2	2021	Temperature	16.5
2	2021	Humidity	42

How to convert long and wide data formats in Python and R

Python Code Example

Wide to Long Format

Python

import pandas as pd

# create wide format data
wide_df = pd.DataFrame({
    'ID': [1, 1, 2, 2],
    'Year': [2020, 2021, 2020, 2021],
    'Temperature': [18.5, 19.0, 17.0, 16.5],
    'Humidity': [30, 32, 40, 42]
})

print(wide_df)

# Convert wide to long format
long_df = pd.melt(
    wide_df, 
    id_vars=['ID', 'Year'], 
    value_vars=['Temperature', 'Humidity'],
    var_name='Measurement', 
    value_name='Value' 
)

print(long_df)

# Convert back to wide format
wide_df = long_df.pivot_table(
    index=['ID', 'Year'], 
    columns='Measurement',
    values='Value'
).reset_index()

print(wide_df)

R Code Example

Wide to Long Format

library(tidyverse)

# wide format data
wide_data <- data.frame(
  ID = c(1, 1, 2, 2),
  Year = c(2020, 2021, 2020, 2021),
  Temperature = c(18.5, 19.0, 17.0, 16.5),
  Humidity = c(30, 32, 40, 42)
)
print(wide_data)

# Convert wide to long format
long_data <- wide_data |>
  pivot_longer(
    cols = c(Temperature, Humidity),
    names_to = "Measurement",
    values_to = "Value"
  )

print(long_data)

# Convert long back to wide format
wide_data <- long_data |>
  pivot_wider(
    id_cols = c(ID, Year),
    names_from = Measurement,
    values_from = Value
  )

print(wide_data)