How-to May 13, 2026

How to extract numbers from text with regex

The patterns for integers, decimals, negatives, currency, and scientific notation — with side-by-side comparisons.

The short answer

For simple integers in a string:

\d+

For most real-world cases (including decimals and negatives):

-?\d+(\.\d+)?

Use matchAll in JavaScript or findall in Python to get all occurrences.

The four common cases

1. Just digits

Pattern: \d+
Input:   "Order #12345 shipped on day 7"
Matches: ["12345", "7"]

Use this when you know there are no decimals or signs to worry about.

2. Decimals (and integers)

Pattern: \d+(\.\d+)?
Input:   "Order $24.99 ships in 3 days"
Matches: ["24.99", "3"]

The (\.\d+)? says: optionally, a dot followed by more digits. Use this for prices, measurements, and other decimal data.

3. Negatives included

Pattern: -?\d+(\.\d+)?
Input:   "Temperature: -12.5°C; humidity: 80"
Matches: ["-12.5", "80"]

4. Scientific notation

Pattern: -?\d+(\.\d+)?([eE][+-]?\d+)?
Input:   "Avogadro: 6.022e23"
Matches: ["6.022e23"]

JavaScript example

const text = "Order #12345 totalling $24.99 ships in 3 days";
const numbers = [...text.matchAll(/-?\d+(\.\d+)?/g)].map(m => parseFloat(m[0]));
// [12345, 24.99, 3]

Python example

import re
text = "Order #12345 totalling $24.99 ships in 3 days"
numbers = [float(m) for m in re.findall(r"-?\d+(?:\.\d+)?", text)]
# [12345.0, 24.99, 3.0]

Gotchas

The minus sign isn't always a negative

-12 in "car-12-door" isn't a negative number — the hyphen is a separator. If you want only true negatives (preceded by whitespace, start of string, or specific characters), use a lookbehind:

(?<=^|\s)-?\d+(\.\d+)?

Dots aren't always decimals

Version numbers like 1.2.3 match 1.2 with the decimal pattern, leaving .3 behind. If your text has version numbers or IP addresses, use word boundaries:

\b\d+(\.\d+)?\b

Commas as thousand separators

For European/US numbers like 1,000,000 or 1.000.000, the pattern needs to handle the separators:

\d{1,3}(,\d{3})*(\.\d+)?       US: 1,234.56
\d{1,3}(\.\d{3})*(,\d+)?        EU: 1.234,56

Currency symbols

If you want the amount including symbol:

[$€£¥]?\s*-?\d+(\.\d+)?

The takeaway

For 80% of cases, -?\d+(\.\d+)? is the right pattern. Add features one at a time as you encounter them — don't reach for the kitchen-sink pattern that handles every case until you actually need to.

For complex parsing (currency strings with locale-specific separators, scientific notation, percentages), parse after the match: use regex to find the number-shaped string, then use a real parser to convert.