BCD & 7-Segment Calculator
Decimal to BCD groups and live 7-segment patterns — common-cathode/anode bytes for every digit, with the RTC 0x12 trap explained.
BCD & 7-Segment Calculator computes decimal numbers as BCD nibbles and live 7-segment drive patterns — free, instant and private in your browser. Clock/meter builders and anyone interfacing displays or RTC chips use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About BCD & 7-Segment Calculator
BCD & 7-Segment Calculator computes decimal numbers as BCD nibbles and live 7-segment drive patterns using the standard engineering relation: one 4-bit group per digit (8421 weights); segment bytes via lookup, inverted for common-anode. Worked live: 147 is BCD 0001 0100 0111; digit 4 lights segments bcfg = 0x66 on common cathode. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use BCD & 7-Segment Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use BCD & 7-Segment Calculator?
- ✓Implements the real formula — one 4-bit group per digit (8421 weights) — with the substitution shown, not a black box
- ✓Built for clock/meter builders and anyone interfacing displays or RTC chips
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate bcd & 7-segment?+
Decimal numbers as BCD nibbles and live 7-segment drive patterns follows one 4-bit group per digit (8421 weights); segment bytes via lookup, inverted for common-anode. For example, 147 is BCD 0001 0100 0111; digit 4 lights segments bcfg = 0x66 on common cathode. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why does my RTC read 18 minutes when the clock shows 12?+
DS1307-class RTCs store time as BCD: register 0x12 means the DIGITS 1 and 2, i.e. twelve. Reading it as plain binary gives 18. Convert with (b>>4)*10 + (b&0x0F) on read and the inverse on write — the most classic RTC bug there is.
Common cathode or common anode — what changes in my code?+
Polarity of everything: CC lights a segment with HIGH, CA with LOW, so the same digit's pattern byte is the bitwise complement. Mixing them shows inverted ghosts (all segments lit except the digit). This tool emits both bytes so you can match the hardware.
Is the BCD & 7-Segment Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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