BCD Converter

Computers count in binary, but humans read decimal, and binary-coded decimal is the compromise that kept both sides happy for decades. In BCD, every decimal digit is stored as its own four-bit binary group: 42 becomes 0100 0010, not the binary value 101010. The cost is wasted patterns — 1010 through 1111 never appear — but the benefit is that decimal digits are directly visible in the bits, which made BCD ideal for calculators, digital clocks, seven-segment displays, and financial systems that could not tolerate binary floating-point rounding. This tool converts decimal numbers to BCD and validates BCD back to decimal, rejecting the invalid digit patterns that pure binary conversion would silently accept.

Quick Answer: Enter 42 and the tool returns 0100 0010.

Free Online Tool

Convert between decimal numbers and binary-coded decimal, where every decimal digit gets its own 4 bits.

Value

Conversion

BCD wastes the bit patterns 1010-1111, but keeps decimal digits readable — handy for displays and clocks.

Table of Contents

How to Use the BCD Converter

Enter your input in the tool above — for example, 42.
Choose any options the tool offers, such as the conversion direction or the settings that fit your case.
Click the main button to run the tool and read the result it displays.
Check the result against what you expected, then adjust the input and run it again if needed.
Copy the output into your own document, code, or configuration wherever you need it.

Worked Example

Try it with 42: the tool returns 0100 0010. That example is a good first test whenever you use the tool, because it confirms you entered the input in the expected format before you trust it with your real values. This tool is built for working with displays, clocks, and decimal-oriented hardware, and the worked example shows the shape of a correct result so you can recognize a wrong one at a glance.

Key Features

Runs entirely in your browser — nothing you type is uploaded anywhere.
Built for working with displays, clocks, and decimal-oriented hardware, with the result shown immediately and in full.
No account, no sign-up, and no software to install.
Clear error messages when an input is incomplete or in the wrong format.
Free to use as often as you like, for study, work, or checking homework.

Best Practices and Tips

Start with the worked example in the guide, then substitute your own values.
Double-check units and formats before trusting a result — most tool errors are input errors.
Keep a note of the exact inputs that produced a result you rely on, so you can reproduce it.
For anything important, cross-check with a second method or a known test value.
Bookmark the tool if you use it regularly, so the same workflow is always one click away.

Common Mistakes to Avoid

Accepting BCD digits 1010-1111, which are not valid decimal digits.
Confusing BCD with plain binary: 42 in BCD is 0100 0010, not 101010.
Copying a result without checking it against a known example first.
Assuming the tool knows your context — it only sees the values you enter.

When This Tool Helps — and When It Doesn’t

This tool helps most when you need a fast, checkable answer for working with displays, clocks, and decimal-oriented hardware and you can verify the result against a known example. It does not replace professional judgment: for decisions with real consequences, treat the output as one input among several, verify it independently, and remember that the tool can only work with exactly what you enter. Used that way — quick check, verified result, human decision — it saves time without creating false confidence.

Frequently Asked Questions

Why waste six bit patterns per digit?

Because readability and exact decimal arithmetic mattered more than density in the systems that used BCD. The wasted patterns are the price of keeping every decimal digit directly visible and exactly representable.

Is BCD still used today?

Yes, in real-time clocks, some financial and point-of-sale hardware, and packed-decimal formats in mainframe systems, where decimal exactness beats binary efficiency.

What is packed BCD?

Packed BCD stores two decimal digits per byte instead of one digit per byte. This tool shows unpacked groups with spaces for readability; removing the spaces gives the packed form.