Farther or further: which is correct?

Correct
farther (physical distance) / further (figurative extent; "additional"; also distance)
Avoid
farther (for "additional" or figurative extent: "farther discussion")
Summary

Correct: farther (physical distance) / further (figurative extent; "additional"; also distance) — Avoid: farther (for "additional" or figurative extent: "farther discussion"). Farther = at or to a greater physical distance; further = to a greater degree or extent, additional, and (especially in British English) also physical distance.

Part of speech
adverb, adjective
Source
Merriam-Webster

Why

Merriam-Webster: farther is preferred for literal distance and further for figurative extent and in the sense of additional (further information); Oxford treats the two as interchangeable for physical distance in British English, but only further carries the figurative senses (further discussion, further information).

Examples

  • We walked two miles farther than planned.
  • The committee asked for further information.
Check your own text: Spell Checker
Catch typos and common misspellings in American or British English, with suggestions, checked right in your browser.
Open tool

Native spelling engine

Checked against
Merriam-Webster / Oxford
Spelling authority
Merriam-Webster · Oxford English Dictionary / Oxford spelling · SCOWL
Commonly confused and non-standard forms
64
Dictionary
Hunspell en_US / en_GB / en_AU / en_CA · Dictionary license: MIT AND BSD (SCOWL combined licence)