HomeConvertersLengthCentimeters to Inches conversion
Length conversion

Centimeters to Inches conversion

Convert between centimeters (cm) and inches (in). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.

Instant result
Result
—

Enter values to convert.

Inputs —
Mode —
Formula —

Formulas

Core equations used by this converter.

cm → inin = cm ÷ 2.54
Exact factor1 in = 2.54 cm
in → cmcm = in × 2.54
iThe international inch is exactly 2.54 centimeters. Prefer dividing by 2.54 over a rounded 0.3937 multiplier when precision matters. Fractional inches in the reference table are rounded to 1/64″.

How to use

1

Choose cm → in or in → cm

Use the tabs to switch direction. Forward mode needs centimeters; reverse mode needs inches.

2

Enter the length

Type a non-negative value in the active unit field.

3

Convert and read the result

Use Convert or let the result update automatically. Check the decimal output; use the reference table for nearest fractions.

Example conversions

Common values with formula and result.

ϟ

10 cm

10 cm ÷ 2.54

10 ÷ 2.54
3.937 in
ϟ

20 cm

20 cm ÷ 2.54

20 ÷ 2.54
7.874 in
ϟ

50 cm

50 cm ÷ 2.54

50 ÷ 2.54
19.685 in
ϟ

100 cm

100 cm ÷ 2.54

100 ÷ 2.54
39.370 in

Centimeters to Inches conversion specification

Version 1.1.0 · Engine tested

Calculation status
  • Engine tested 5 published cases
  • Named expert review Not performed
  • Calculation version 1.1.0

Review policy

Definition
The centimeter (cm) is a metric length unit (100 cm = 1 m; 10 mm = 1 cm). The inch (in) is an imperial/US customary unit defined as exactly 2.54 cm. This converter turns centimeters into inches using that exact international factor.
What it calculates
Length between centimeters and inches using the exact international inch definition. Switch direction with the cm → in / in → cm tabs.
Inputs
  • Length in centimeters (cm) or inches (in), depending on selected tab
Outputs
  • Converted length in the opposite unit (decimal)
  • Nearest fraction from the reference chart (1/64″), when using the table
Formula
in = cm ÷ 2.54 · cm = in × 2.54 · 1 in = 2.54 cm exactly
cm → in chart (1/64″ fractions)
Centimeters (cm)Inches (decimal)Inches (fraction)
0.1 cm0.0394 in3/64 in
1 cm0.3937 in25/64 in
2 cm0.7874 in25/32 in
3 cm1.1811 in1 3/16 in
5 cm1.9685 in1 31/32 in
10 cm3.9370 in3 15/16 in
15 cm5.9055 in5 29/32 in
20 cm7.8740 in7 7/8 in
25 cm9.8425 in9 27/32 in
30 cm11.8110 in11 13/16 in
50 cm19.6850 in19 11/16 in
60 cm23.6220 in23 5/8 in
100 cm39.3701 in39 3/8 in
i Fractions rounded to 1/64″. Woodworking often uses 1/16″ or 1/8″ instead.
Assumptions
  • Uses the international inch: 1 in = 2.54 cm exactly.
  • Conversion runs locally in the browser; values are not uploaded.
  • Fractional inches in the reference table are rounded to 1/64″ resolution.
Units
  • cm → in
  • in → cm
Boundary conditions
  • Empty or non-numeric input yields no valid result.
  • Zero centimeters converts to zero inches.
  • Very large values follow the same linear factor (no unit wrap).
Example
20 cm → 7.874015748… in ≈ 7.874 in
Validation cases
  • 1 cm → 0.3937007874 in
  • 2.54 cm → 1 in
  • 10 cm → 3.937007874 in
  • 20 cm → 7.874015748 in
  • 100 cm → 39.37007874 in
Sources
  • International yard and pound agreement: 1 in = 2.54 cm exactly
  • SI relation: 100 cm = 1 m; 10 mm = 1 cm
Calculation version
1.1.0

Background

Interpretation and common distinctions.

Manual check and reverse

Sanity check: 2.54 cm must equal exactly 1 in.

2.54/2.54 = 1 in

Reverse (inches → centimeters):

d(cm) = dᵢₙ × 2.54

Use the in → cm tab above, or open inches to centimeters.

Related length units

Unit System Relation
cm Metric 10 mm = 1 cm; 100 cm = 1 m
in Imperial / US 1 in = 2.54 cm = 25.4 mm
mm Metric 1 mm = 0.1 cm = 1/25.4 in

For finer metric steps: cm to mm · mm to inches.

ft Centimeters to feet › mm Centimeters to millimeters › cm Inches to centimeters › in Millimeters to inches › ft Height converter ›

Frequently asked questions

Key distinctions behind the conversion.

How do you convert centimeters to inches?

Divide centimeters by 2.54. Equivalently, multiply by ≈ 0.3937007874. Example: 20 cm ÷ 2.54 ≈ 7.874 in.

How many inches is 1 cm?

Exactly 1/2.54 inches, about 0.3937007874 in (often rounded to 0.3937 in).

Is 2.54 cm per inch exact?

Yes. By international agreement the inch is defined as exactly 2.54 centimeters.

How do I convert inches back to centimeters?

Switch to the in → cm tab and multiply inches by 2.54, or open the dedicated Inches to centimeters page.

When should I use fractional inches?

Woodworking and construction often round to 1/16″ or 1/8″. The reference table on this page shows nearest 1/64″ for finer matching.

Can I convert negative lengths?

The factor still applies mathematically, but length conversions are normally used with non-negative values.