diff --git a/flit/sdist_rules.py b/flit/sdist_rules.py
new file mode 100644
index 00000000..45d3449b
--- /dev/null
+++ b/flit/sdist_rules.py
@@ -0,0 +1,120 @@
+"""Generate sdist include/exclude rules for Flit
+
+To use: cd into a folder with pyproject.toml set up for Flit, inside a git
+repository. Produce any files that should be excluded (e.g. build docs).
+Run 'python -m flit.sdist_rules'. It aims to include all files that are tracked
+in git, with as few patterns as feasible.
+
+The output is TOML formatted to be used in pyproject.toml - feel free to add or
+remove includes & excludes manually.
+"""
+
+import argparse
+import glob
+import sys
+from pathlib import Path
+
+import tomli_w
+
+from flit_core.common import Module
+from flit_core.config import read_flit_config
+from .vcs.git import list_tracked_files
+
+def read_gitignore(path: Path):
+    rules = []
+    for line in path.read_text('utf-8').splitlines(keepends=False):
+        if (not line.strip()) or line.startswith('#'):
+            continue  # Blank line or comment
+
+    exclude = True
+    if line.startswith('!'):
+        exclude = False
+        line = line[1:]
+
+    # TODO: backslash escaping?
+    rules.append((exclude, glob.translate(line)))
+
+
+def is_ignored(path: Path, rules):
+    # A later ! rule can re-include an excluded file, so we need to evaluate
+    # all the rules
+    ignored = False
+    for exclude, pattern in rules:
+        if pattern.match(path):
+            ignored = exclude
+
+    return ignored
+
+
+def auto_exclude(p: Path):
+    """Check if a path will be excluded regardless of config"""
+    return p.name == '__pycache__' or p.suffix == '.pyc'
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--debug", action="store_true")
+    args = ap.parse_args()
+
+    def debug(*a):
+        if args.debug:
+            print(*a, file=sys.stderr)
+
+    pyproj_file = Path("pyproject.toml")
+    config = read_flit_config(pyproj_file)
+    module = Module(config.module)
+
+    auto_inc_files = [pyproj_file] + [Path(s) for s in config.referenced_files]
+    auto_inc_dirs = []
+    if module.is_package:
+        auto_inc_dirs.append(module.path)
+    else:
+        auto_inc_files.append(module.path)
+    if config.data_directory is not None:
+        auto_inc_dirs.append(config.data_directory)
+
+    def auto_include(p: Path):
+        return p in auto_inc_files or any(p.is_relative_to(d) for d in auto_inc_dirs)
+
+    includes = [p for s in list_tracked_files(".") if not auto_include(p := Path(s))]
+    debug(f"{len(includes)} additional files to include in sdist")
+
+    # For each directory containing included files, does including the directory
+    # and excluding ignored files mean fewer rules overall
+    candidate_dirs = set()
+    for path in includes:
+        candidate_dirs.update(path.parents[:-1])  # slice off Path(".")
+
+    new_includes = set(includes)
+    new_excludes = set()
+
+    for dir in sorted(candidate_dirs, key=lambda p: (-len(p.parts), p)):
+        debug(f"Evaluating {dir}")
+        included_matches = [p for p in new_includes if p.is_relative_to(dir)]
+        add_excludes = [p for p in dir.iterdir()
+                        if p not in included_matches and not auto_exclude(p)]
+
+        debug(f"Could replace {len(included_matches)} includes: "
+              f"{[str(p.relative_to(dir)) for p in included_matches]}")
+        debug(f"Would require {len(add_excludes)} additional excludes: "
+              f"{[str(p.relative_to(dir)) for p in add_excludes]}")
+        if len(included_matches) > len(add_excludes):
+            debug("Replacing")
+            new_includes -= set(included_matches)
+            new_includes.add(dir)
+            new_excludes |= set(add_excludes)
+        debug()
+
+    def fmt_path(p: Path) -> str:
+        return p.as_posix() + ('/' if p.is_dir() else '')
+
+    print("# The TOML table below can be copied into your pyproject.toml\n")
+    print("[tool.flit.sdist]")
+    print(tomli_w.dumps({
+        "include": sorted([fmt_path(p) for p in new_includes], key=str.lower),
+        "exclude": sorted([fmt_path(p) for p in new_excludes], key=str.lower),
+    }))
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/flit_core/pyproject.toml b/flit_core/pyproject.toml
index 352336d7..bf46bf08 100644
--- a/flit_core/pyproject.toml
+++ b/flit_core/pyproject.toml
@@ -28,4 +28,5 @@ include = [
     "bootstrap_install.py",
     "build_dists.py",
     "tests_core/",
+    "update-vendored-tomli.sh",
 ]
diff --git a/pyproject.toml b/pyproject.toml
index 23514cf8..379b0aa7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,3 +45,26 @@ Changelog = "https://flit.pypa.io/en/stable/history.html"
 
 [project.scripts]
 flit = "flit:main"
+
+[tool.flit.sdist]  # Generated with python -m flit.sdist_rules
+include = [
+    ".bumpversion.cfg",
+    ".coveragerc",
+    ".github/",
+    ".gitignore",
+    ".pre-commit-config.yaml",
+    ".readthedocs.yml",
+    "bootstrap_dev.py",
+    "codecov.yml",
+    "doc/",
+    "flit_core/",
+    "prepare_license_list.py",
+    "SECURITY.md",
+    "tests/",
+    "tox.ini",
+]
+exclude = [
+    "doc/_build/",
+    "flit_core/.pytest_cache/",
+    "flit_core/dist/",
+]