Fixing Python xlsxwriter That Truncates Long Text in Wrapped Cells

You set text_wrap on a format, write a long string to a cell, open the file in Excel, and the text is still cut off at the bottom. The wrap is happening — you can see the line breaks — but the row isn't tall enough to show all the lines. This is one of xlsxwriter's most common gotchas, and the fix requires a bit of arithmetic.

The Problem: Text Wraps but Still Gets Cut Off

xlsxwriter does not automatically resize row height when you enable text wrapping. Excel itself can do this interactively when you double-click a row border, but xlsxwriter writes a static file. Whatever row height you set (or don't set) is baked in. If you don't explicitly calculate and assign the height, Excel uses its default — typically 15 points — which shows only a single line of text.

The frustrating part is that the wrap format is working. Excel renders the text on multiple lines inside the cell; it just clips anything below the default row height. Open the file, press Ctrl+A, and then auto-fit rows — the text appears instantly. The data was always there.

What You'll Learn

• Why xlsxwriter can't auto-expand row height and what you must do instead
• How to estimate the number of wrapped lines a string produces given a column width
• How to call set_row() with the correct height in points
• How to handle multiple wrapped columns in the same row
• A reusable helper function you can drop into any reporting script

Prerequisites

• Python 3.8 or newer
• xlsxwriter installed (pip install xlsxwriter)
• Basic familiarity with xlsxwriter's Workbook, Worksheet, and Format objects

Why xlsxwriter Doesn't Auto-Expand Row Height

xlsxwriter is a write-only library. It generates the XML that makes up an .xlsx file, but it never reads an existing file and has no rendering engine to measure how text flows inside a cell. Excel calculates wrap height at render time, taking into account the font, font size, column width in pixels, DPI, and zoom level. xlsxwriter has none of that information unless you supply it.

The text_wrap property in the format object simply sets a flag in the cell's XML. The actual row height in the file stays at whatever default or explicit value you provided. If you write nothing, it stays at 15 points — one line for the default 11pt Calibri font.

This is not a bug. It's a fundamental constraint of a write-only approach. The fix is to compute the height yourself before calling worksheet.set_row().

How to Calculate the Required Row Height

The calculation involves three pieces of information: the length of your string, the column width in characters, and the font size in points.

Column width in xlsxwriter is measured in "character units" — roughly the width of the digit 0 in the default font. A column set to width 20 can display about 20 characters per line. To estimate how many lines a string needs:

import math

def estimate_line_count(text: str, col_width: float) -> int:
    """Estimate the number of lines text occupies in a wrapped cell."""
    if not text:
        return 1
    # Split on existing newlines first, then wrap each segment
    lines = 0
    for segment in str(text).split("\n"):
        # Each segment wraps at approximately col_width characters
        lines += max(1, math.ceil(len(segment) / col_width))
    return lines

This is an approximation. Proportional fonts mean that "WWWW" is wider than "iiii" even at the same character count. For most business text — sentences, addresses, notes — this estimate is close enough. If you're dealing with heavily mixed-width characters or a non-default font, you may need to add a small padding multiplier (e.g., multiply by 1.1).

Once you have the line count, convert it to points. Excel's default line height for a standard 11pt font is roughly 15 points. A safe formula is:

def row_height_for_lines(line_count: int, font_size_pt: float = 11) -> float:
    """Return a row height in points to fit the given number of lines."""
    # Empirical multiplier: line height is roughly 1.4x the font size
    line_height = font_size_pt * 1.4
    # Add a small top/bottom margin
    return max(15, line_height * line_count + 2)

The max(15, ...) guard ensures the row is never shorter than Excel's default, which keeps single-line rows looking normal.

Setting Row Height Manually with set_row()

With those helpers in place, the write loop becomes straightforward. Here's a minimal working example:

import xlsxwriter
import math

COL_WIDTH = 40  # characters
FONT_SIZE = 11  # points

def estimate_line_count(text, col_width):
    if not text:
        return 1
    lines = 0
    for segment in str(text).split("\n"):
        lines += max(1, math.ceil(len(segment) / col_width))
    return lines

def row_height_for_lines(line_count, font_size_pt=11):
    line_height = font_size_pt * 1.4
    return max(15, line_height * line_count + 2)

data = [
    "Short text",
    "This is a much longer piece of text that will definitely need to wrap across several lines inside the cell when the column width is only forty characters.",
    "Another long note:\nThis one already has\na manual newline in it.",
]

workbook = xlsxwriter.Workbook("wrapped_output.xlsx")
worksheet = workbook.add_worksheet()

wrap_format = workbook.add_format({
    "text_wrap": True,
    "valign": "top",
})

worksheet.set_column(0, 0, COL_WIDTH)

for row_idx, cell_text in enumerate(data):
    worksheet.write(row_idx, 0, cell_text, wrap_format)
    lines = estimate_line_count(cell_text, COL_WIDTH)
    height = row_height_for_lines(lines, FONT_SIZE)
    worksheet.set_row(row_idx, height)

workbook.close()
print("Done — all rows sized correctly.")

Open wrapped_output.xlsx and every row will be tall enough to show its full text without clipping. Note the valign: top in the format — without vertical alignment set to top, long text in a tall row will be vertically centered, which looks odd in most report layouts.

Handling Multiple Columns With Wrapped Text

When more than one column in a row contains wrapped text, you need the height that accommodates the tallest cell. Compute the line count for each wrapped column and take the maximum before calling set_row().

col_widths = {0: 30, 1: 20, 2: 50}  # column index -> width in chars

rows = [
    ("A short label", "Another medium-length description that might wrap", "A very detailed note that is the longest of the three columns and will need the most vertical space to display correctly."),
    ("Label B", "Brief", "Also brief"),
]

for row_idx, row_data in enumerate(rows):
    max_lines = 1
    for col_idx, cell_text in enumerate(row_data):
        width = col_widths.get(col_idx, 20)
        lines = estimate_line_count(cell_text, width)
        max_lines = max(max_lines, lines)
        worksheet.write(row_idx, col_idx, cell_text, wrap_format)
    worksheet.set_row(row_idx, row_height_for_lines(max_lines, FONT_SIZE))

The key insight is that set_row() applies a single height to the whole row, so you always need the worst-case column driving the calculation.

Dealing with Merged Cells and Wrapped Text

Merged cells add a layer of complexity. When you merge a range of rows, Excel distributes the text display across those rows. xlsxwriter's merge_range() still writes to the file's XML as a single cell spanning the rows, but row height needs to account for the merged span.

If you're merging columns horizontally (e.g., A1:C1), the effective column width for wrapping purposes is the sum of the individual column widths. Use that combined width in estimate_line_count() for a reasonable estimate. For vertical merges, the height calculation becomes significantly more complex, and the simplest practical solution is to add a generous fixed height or accept that the user may need to manually expand the row in rare edge cases.

If merged cells are a core part of your report, see the related guide on how xlsxwriter handles cell formats on merged cells — the formatting behaviour there interacts directly with wrap settings.

A Reusable Helper Function

Rather than repeating this logic in every script, package it into a small utility. Here's a version that accepts a list of (text, col_width) tuples for all wrapped columns in a row and returns the height to set:

import math

def calculate_row_height(
    wrapped_cells: list[tuple[str, float]],
    font_size_pt: float = 11,
    padding_pt: float = 2,
) -> float:
    """
    Calculate the row height needed to display all wrapped cells.

    Args:
        wrapped_cells: list of (text, col_width_chars) pairs
        font_size_pt: font size in points (default 11)
        padding_pt: extra padding added to the total height

    Returns:
        Row height in points, minimum 15.
    """
    max_lines = 1
    for text, col_width in wrapped_cells:
        lines = 0
        for segment in str(text).split("\n"):
            lines += max(1, math.ceil(len(segment) / col_width))
        max_lines = max(max_lines, lines)

    line_height = font_size_pt * 1.4
    return max(15.0, line_height * max_lines + padding_pt)

Call it like this in your write loop:

height = calculate_row_height(
    [(row["notes"], 40), (row["description"], 30)],
    font_size_pt=11,
)
worksheet.set_row(row_idx, height)

This pattern scales cleanly to reports with dozens of columns — you only pass the columns that have text_wrap enabled.

If your project also uses openpyxl for reading or editing existing files, the approach differs slightly. The guide on fixing openpyxl's column width autofitting shows the equivalent technique for that library.

Common Pitfalls and Gotchas

Forgetting to set column width before calculating

If you call worksheet.set_column() after set_row(), the column width is still applied correctly in the file — xlsxwriter processes these independently. But if you're using the column width variable in your height calculation, make sure that variable is set before you compute line counts. This is a code-flow issue, not a library issue.

Using the wrong unit for font size

xlsxwriter's font_size in format options is in points. The multiplier of 1.4 in the helper assumes points as well. If you pull font size from a config in some other unit, convert it first or you'll get wildly wrong heights.

Non-ASCII characters and proportional fonts

The character-count estimate works well for ASCII text in proportional fonts like Calibri because letters are roughly average width. It breaks down for CJK (Chinese, Japanese, Korean) text, where each character is roughly double the width of a Latin character. For CJK content, use a multiplier of 2 on the character count before dividing by column width.

Assuming text_wrap also sets valign

text_wrap: True does not set vertical alignment. Without valign: "top", text in a taller-than-default row will sit in the vertical center or bottom of the cell depending on your Excel version's defaults. Always pair text_wrap with an explicit valign.

Numbers and dates written as wrapped cells

Applying a text_wrap format to numeric or date cells does not convert them to strings in the file — xlsxwriter writes them as their native type. But if you've previously had issues with numbers being stored as text, the separate problem of xlsxwriter writing numbers as text and breaking SUM formulas is worth reading to avoid mixing up the two issues.

Large datasets and performance

Running estimate_line_count() in Python for every row in a 50,000-row export is fast — it's just integer arithmetic. The bottleneck will be the xlsxwriter write calls, not the height computation. No need to cache or batch the height calculations.

Next Steps

• Add the calculate_row_height() helper to a shared excel_utils.py module and import it in all your reporting scripts.
• If your reports use charts alongside data, check that your chart data ranges still resolve correctly — blank chart rendering after writing data is a common companion issue.
• Test your output with both the desktop Excel client and Excel Online; row height rendering can differ slightly between them, so adding 10–15% extra padding to row_height_for_lines() provides a comfortable safety margin.
• For reports where column widths themselves need to auto-fit to content, consider combining this technique with a column-width estimation pass before you open the workbook.
• If your pipeline reads Excel files back in after writing them, confirm that pandas reads the rows correctly regardless of height — row height is purely visual and has no effect on data parsing.