Resistor Band Calculator. Decode a recorded 3-, 4-, 5-, or 6-band IEC-style resistor marking, or exactly encode nominal ohms without rounding, nearest-series substitution, or circuit-safety claims.
Specialist tool for Electronics2 documented formulasFocused single-task workflowPrivate in your browser
Use this result well
A quick decision brief for this specific tool
Inputs that matter
Decode: selected 3/4/5/6-band system, an explicit observed first-to-last orientation basis, bounded marking/product context, two or three ordered significant-band colours, one supported multiplier colour, the applicable no-band/explicit tolerance colour and optional sixth-band TCR colour. Exact encode: selected band system, exact nominal resistance in ohms, applicable tolerance colour and optional sixth-band TCR colour
Output to expect
Decode: ordered code, exact nominal ohms with SI-prefixed display, significant integer/multiplier, nominal tolerance interval and optional TCR. Encode: an exact ordered colour code only when the target fits the supported digit/multiplier set, plus the same transparent resistance/tolerance/TCR record
How it works
Validate the selected system and observed order, reject a leading black significant band and unresolved orientation, use two digits for 3/4-band or three for 5/6-band, multiply by the exact colour exponent, derive ±20% only for no-band 3-band records, append explicit tolerance/TCR only when applicable, and for encoding search only exact integer-significant representations across supported multipliers without rounding or preferred-series substitution
Confirm the exact physical order, colours, band count, component/product marking convention and manufacturer applicability. A single black zero-ohm link, non-resistor marking, ambiguous orientation, faded colour, special reliability/material marking or unsupported product-specific tolerance/TCR code needs another source or workflow.
Use the result only as marking translation. It does not identify the component, prove nominal or measured resistance, tolerance, TCR, condition or drift; establish E-series membership or availability; select a resistor; determine power, voltage, pulse, frequency, thermal or circuit suitability; validate a design or repair; or authorize energizing, probing, purchase, installation or use. Follow exact component/meter instructions, de-energize, discharge stored energy and control parallel paths/lead resistance for measurement.
Choose your path
Built around the job you need to finish
Decode one explicitly ordered 3/4/5/6-band IEC-style axial-resistor marking or exactly encode one entered nominal resistance without guessing orientation, rounding to a preferred value, identifying a component or approving a circuit decision.
Repair technician documenting a removed axial resistor
Translate a recorded marking without treating color arithmetic as proof of part identity, condition, rating or repair suitability.
De-energize and control stored energy under the service procedure, remove or isolate as required, record component context and first-to-last observation, decode the marking, then retain measurement and replacement evidence separately.
Gets exact nominal/tolerance/TCR marking arithmetic and an explicit stop boundary for ambiguous order, measurement, ratings, root cause, replacement selection and repair approval.
Engineer preparing an exact candidate marking record
Express an exact nominal value as 3/4/5/6 bands without silent rounding or a fabricated nearest component recommendation.
Choose the intended band system, enter exact ohms plus tolerance and optional TCR, accept a code only when the digit/multiplier set represents it exactly, then verify preferred series and manufacturer product data outside the Tool.
Receives a reproducible exact code or a clear nonrepresentable-value error while E-series, stock, package, ratings, derating and circuit suitability remain separate decisions.
Teach two-versus-three significant digits, implicit no-band tolerance, TCR and ambiguity without embedding unsafe shortcuts.
Compare 3/4/5/6-band examples, test leading-black and unresolved-orientation errors, inspect exact steps and export only intentionally committed records.
Students can reproduce marking arithmetic and explain why a single black zero-ohm link, uncertain color/order, measurement and component selection need separate evidence.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
Three and four bands use two significant digits; five and six bands use three. Record how first-to-last order was observed. End position, a larger tolerance-side gap, and a manufacturer record can be cues, but the Tool rejects unresolved orientation instead of guessing.
Decode only the selected marking fields
Join the significant digits and multiply by the selected decimal multiplier. A three-band record has no tolerance band and uses implicit ±20%; four and five bands add tolerance, and six bands add a supported TCR marking.
Exact Encode returns a code only when the target fits two or three whole significant digits and one supported multiplier. It does not round, choose a nearest preferred E-series value, check availability, or recommend a product.
Verify the component and work controls separately
Color arithmetic does not prove component type, value, tolerance, TCR, condition, drift, power or voltage rating, or circuit suitability. For measurement, follow the exact component and meter instructions, turn circuit power off, discharge stored energy, and account for parallel paths and test-lead resistance.
Updated: August 2026
Example Scenarios
Record first-to-last colors and the product/circuit reference, decode the marking, then keep de-energized measurement, part identification, ratings, root cause, replacement selection, and repair approval in the controlled service process.
Encode an exact nominal value, tolerance, and optional TCR for documentation, then confirm preferred series, exact manufacturer product, availability, ratings, derating, pulse/frequency/thermal behavior, and circuit performance separately.
Compare 3/4-band two-digit and 5/6-band three-digit arithmetic, demonstrate explicit no-band tolerance and sixth-band TCR, and show why ambiguous order or a leading black digit must not be silently accepted.
Common Mistakes to Avoid
✕
Treating the first visible band as proven orientation
✓
Record an observed end/gap cue or exact manufacturer/product convention. If the order remains unresolved, stop instead of decoding both directions and choosing a convenient answer.
✕
Using a four-band formula for a five- or six-band marking
✓
Five and six bands use three significant digits before the multiplier; six adds TCR after tolerance. Select the observed system first.
✕
Rounding a target and calling the returned colors exact
✓
Use Exact Encode only when the entered ohms fit the selected digits and multiplier exactly. Handle preferred-value and product selection as a separate controlled decision.
✕
Treating nominal colors as measured value, rating, or circuit approval
✓
Confirm the exact product, markings, datasheet ratings, condition, calibrated/de-energized measurement, circuit analysis, protection, derating, and work authorization separately.
FAQ
Three bands are two digits plus multiplier with implicit ±20%. Four bands add tolerance. Five bands use three digits plus multiplier and tolerance. Six bands add a supported TCR field to that five-band structure.
A normal multi-band value cannot begin with a zero significant digit. A single black band can mark a distinct zero-ohm link, which is outside this 3–6-band resistor-value workflow.
The selected system has only two or three significant digits and a finite multiplier set. A rejected value would require rounding or another representation; this Tool never substitutes a nearest E-series value.
No. IEC 60063 preferred series, manufacturer ranges, stock, tolerance, TCR, package, ratings, and availability are separate product-selection evidence.
Use the physical end/gap cues only as observations and confirm the exact product marking convention. If order or color remains ambiguous, stop this decode; do not force a value from guesswork.
Only under the exact meter, component, circuit, and safe-work instructions. Turn circuit power off, discharge stored energy, prefer isolating the component where applicable, and account for parallel circuit paths and lead/contact resistance.
About Resistor Band Calculator
Translate one explicitly ordered IEC-style axial-resistor marking or create an exact candidate marking for entered nominal ohms. Choose the 3/4/5/6-band system, preserve how order was established, and keep product identity, ratings, measurement, circuit design, component selection, and electrical safety outside the color arithmetic.
