Length Converter Tools – Convert cm, mm, m, inches, feet, yards, miles & km
Welcome to the length conversion hub—your one place to convert between centimeters, millimeters, meters, inches, feet, yards, miles, and kilometers. Every calculator uses exact constants, instant math, and a consistent, mobile-first interface.
Whether you’re drafting a room layout, preparing fabrication cut lists, writing product specs, or planning a road trip, consistent units are essential. Our tools centralize precise constants, convert with full precision, and recommend rounding once at output so your PDFs, emails, and CSV exports stay in agreement.
For team workflows, pick a canonical unit (meters for engineering, millimeters for CAD/CAM) and derive other units at the edges for UI and reports. Each page below includes the exact formula, example walkthroughs, best-practice rounding, and context for when to use each unit.
CM to Meters
Convert centimeters to meters (m = cm ÷ 100).
Meters to CM
Convert meters to centimeters (cm = m × 100).
CM to MM
Convert centimeters to millimeters (mm = cm × 10).
MM to CM
Convert millimeters to centimeters (cm = mm ÷ 10).
CM to Inches
Centimeters to inches (exact: 1 in = 2.54 cm).
Inches to CM
Inches to centimeters (cm = in × 2.54).
Inches to Meters
Convert inches to meters precisely.
Meters to Inches
Convert meters to inches (in = m ÷ 0.0254).
CM to Feet
Centimeters to feet (exact: 1 ft = 0.3048 m).
Feet to CM
Feet to centimeters (cm = ft × 30.48).
Meters to Feet
Meters to feet (ft = m ÷ 0.3048).
Feet to Meters
Feet to meters (m = ft × 0.3048).
Inches to Feet
Convert inches to feet (ft = in ÷ 12).
Feet to Inches
Convert feet to inches (in = ft × 12).
Meters to Yards
Meters to yards (exact: 1 yd = 0.9144 m).
Yards to Meters
Yards to meters (m = yd × 0.9144).
Inches to Yards
Inches to yards (yd = in ÷ 36).
Feet to Yards
Feet to yards (yd = ft ÷ 3).
Yards to Feet
Yards to feet (ft = yd × 3).
Yards to Inches
Yards to inches (in = yd × 36).
KM to Miles
Kilometers to miles (mi = km ÷ 1.609344).
Miles to KM
Miles to kilometers (km = mi × 1.609344).
Miles to Feet
Convert miles to feet (ft = mi × 5280).
Why Exact Length Conversions Matter
Tiny rounding differences can snowball as values flow through multiple
layers—browser UI, CAD drawings, emails, PDFs, and analytics. Using exact definitions—for example, inch = 0.0254 m, foot = 0.3048 m,
yard = 0.9144 m, mile = 1609.344 m, centimeter =
0.01 m, millimeter = 0.001 m—and rounding once
at presentation preserves consistency across every surface.
Core Relationships You’ll Use Daily
-
m = cm ÷ 100•cm = m × 100•mm = cm × 10•cm = mm ÷ 10(exact) in = cm ÷ 2.54•cm = in × 2.54(exact)-
ft = m ÷ 0.3048•m = ft × 0.3048(exact) -
yd = m ÷ 0.9144•m = yd × 0.9144(exact) -
mi = km ÷ 1.609344•km = mi × 1.609344(exact; international mile) -
ft = mi × 5280•yd = ft ÷ 3•in = ft × 12(exact)
Rounding, Precision & Display Strategy
Keep calculations at full precision. For consumer specs, two decimals in meters and whole centimeters often strike the right balance. For drawings and QA, align precision with instrument resolution and scale (e.g., 3–4 decimals for intermediate math). Publish a short methods note so teams apply the same policy across PDFs, dashboards, and exports.
Formatting matters: use locale-aware separators and always label units in headers—“Length (cm)”, “Span (m)”— so numbers remain unambiguous in screenshots and CSVs.
Data Modeling & Developer Tips
Choose one canonical unit (m or mm), store it
consistently, and convert at the edges. Use explicit, unit-suffixed fields
like length_m and length_in. Centralize constants in a
utility and maintain a small regression set of known pairs (e.g., 1 m =
100 cm; 1 yd = 0.9144 m). Test both directions in CI to prevent
regressions.
If your app also covers area/volume, keep those calculators separate: length → area/volume requires geometry, and mixing them can create subtle mistakes in specs and quotes.
Regional Conventions & Accessibility
US audiences are comfortable with inches/feet/yards, while international teams prefer metric. Present the local unit while keeping metric canonical underneath. For accessibility, ensure unit text is readable in high-contrast modes and that screen readers can announce both numbers and units.
Common Use Cases
- Architecture & interiors (room dimensions in meters/feet; furniture in cm/inches)
- Fabrication & CNC (mm for tolerances; consumer docs in cm/inches)
- E-commerce specs (cm and inches side-by-side for global shoppers)
- Education & science (SI-centric lesson plans with exact constants)
- Logistics & navigation (km ↔ mi for roads; NM handled separately for marine/aviation)
Worked Examples
Furniture listing: A desk is 120 cm wide. Divide by 100 to get 1.2 m; divide by 2.54 to get ≈ 47.24 in. Show 120 cm and 47.2 in on the card; keep meters canonical in storage.
Site plan: A corridor spans 9.144 m. Divide by 0.3048 to get exactly 30 ft. Present 9.144 m on the drawing and 30 ft in the US spec sheet.
Road distance: A route is 250 km. Divide by 1.609344 to get ≈ 155.343 mi. For signage, round appropriately; retain the precise value for analytics.
Frequently Asked Questions
What are the exact relationships between common metric units?
Metric uses powers of ten: 1 m = 100 cm, 1 cm = 10 mm, and 1 km = 1000 m. These are exact definitions, so you can sum or scale measurements in one unit and convert later without fear of hidden approximations.
Are inch, foot, and yard exact in meters?
Yes. International definitions fix them exactly: 1 inch = 0.0254 m, 1 foot = 0.3048 m, and 1 yard = 0.9144 m. Using these exact factors keeps drawings, datasheets, and exports consistent across tools.
Is a mile exactly defined in kilometers?
The international mile is exactly 1609.344 meters, so 1 mi = 1.609344 km. (Nautical miles are different: 1 NM = 1852 m and belong to navigation contexts.) Keep road miles and nautical miles separate to avoid confusion.
Which unit should I store in my database as canonical?
Most engineering and analytics teams store meters for canonical length. For fabrication and CAD/CAM pipelines, millimeters are also common. Choose one, document it, and convert at the edges to cm, inches, feet, or yards for UI and reports.
How should I handle rounding for drawings and consumer pages?
Compute with full precision internally. For consumer pages, show 1–2 decimals in meters and whole cm/mm where it improves legibility. For CAD/QA, match instrument resolution. Round once at output to keep PDFs and CSVs aligned.
What causes unit drift between CAD drawings and exported spreadsheets?
Double-rounding at multiple layers, mixing stored units across rows, and using approximate constants are frequent culprits. Centralize constants, store a canonical unit, and round once at presentation/export.
Do these tools convert area and volume too?
This hub is for linear length. For area use cm², m², ft², yd²; for volume use m³ or liters. Length-to-area/volume conversions require geometry and should be handled by dedicated calculators.
How do I make my measurements accessible and internationalized?
Always include unit symbols in labels (e.g., “Length (cm)”), use locale-aware number formatting, and ensure strong color contrast. Avoid embedding units as images so screen readers can announce them properly.
Any quick mental math tips for common conversions?
Remember anchors: 1 in = 2.54 cm, 30 cm ≈ 1 ft, 3.281 ft ≈ 1 m, and 1 km ≈ 0.621 mi. These help you sanity-check results before you paste values into drawings or quotes.
How should I name fields for analytics and exports?
Prefer explicit unit-suffixed columns like length_m, length_cm, length_in. Add a methods note in docs: “Exact constants; round once at presentation.” That single paragraph prevents a lot of confusion across teams.
When do centimeters beat meters in UI?
Use centimeters for consumer-facing specs—furniture, garments, and DIY—where whole numbers are easier to scan. Keep meters canonical for summaries, site plans, and system integrations.
Do I need to worry about the US survey foot?
Many jurisdictions deprecated the US survey foot in favor of the international foot (exactly 0.3048 m). Unless you work with historic survey data, stick to the international definitions used here.
How can I validate conversions in an automated way?
Create a small regression set of known pairs (e.g., 1 m = 100 cm; 1 yd = 0.9144 m; 1 mi = 5280 ft) and test both directions in CI. This catches accidental constant changes and formatting regressions early.
Can I mix metric and imperial in one column?
Avoid mixing. Store a single canonical unit and derive others for display. If you must accept mixed input, normalize on write and keep the original text as a separate field for audit purposes.
Keep This Page Handy
Bookmark this category page for rapid access to every length converter on MetricCalc. New tools will follow the same layout and rounding philosophy so you can switch units without relearning the interface. If a unit pair is missing, tell us and we’ll build it to the same exacting standards.