Resistor Color Code Calculator

Read the value, tolerance and temperature coefficient of a 4-, 5- or 6-band resistor from its colours, or find the bands for a value, using the IEC 60062 colour code.

Method, formulas and references

Reading the bands

Hold the resistor with the tolerance band on the right. That band usually stands a little apart from the others, and gold or silver never appears on the left: they are only multipliers or tolerances.

4 bands: two digits, multiplier, tolerance. Yellow, violet, red, gold = 47 × 100 Ω = 4.7 kΩ ±5 %.
5 bands: three digits, multiplier, tolerance, used for 1 % and better parts. Brown, black, black, brown, brown = 100 × 10 Ω = 1 kΩ ±1 %.
6 bands: as 5 bands plus the temperature coefficient (TCR) in ppm/K.
3 bands: a 4-band code with no tolerance band, which means ±20 %.

(1)R = (digits) × 10^multiplier Ω

Gold multiplies by 0.1, silver by 0.01 and pink by 0.001. A single black band marks a zero-ohm link. The colours follow IEC 60062:2016. Before that edition some manufacturers used grey for ±0.05 %; the standard now assigns grey to ±0.01 %.

Finding the colours for a value

The value is rounded to two significant digits for 4 bands or three for 5 and 6 bands. Values from the E12 and E24 series fit in two digits; E96 values need three. The result lists the IEC 60063 series that contain the value.

References

IEC 60062:2016, Marking codes for resistors and capacitors.
IEC 60063:2015, Preferred number series for resistors and capacitors.

Related components tools

All calculators

Signal integrity

Impedance Calculator – Single-ended and differential microstrip, coated and embedded microstrip, stripline and coplanar lines, solved with a 2D field solver.
Propagation Delay, εeff & Timing – Propagation delay, length matching from skew, rise time to bandwidth, critical length and wavelength.
Signal Termination Calculator – Source-series, single-ended load and differential load termination from trace impedance, with E-series values, reflection and resistor stress.
Trace Loss (Insertion Loss) Calculator – Insertion loss in dB/in and over the full length: conductor loss with copper roughness and dielectric loss from the field solver, with laminate Dk/Df across frequency.
Crosstalk Calculator – Near- and far-end crosstalk between parallel traces from the field solver, with a sweep over the spacing (3W rule check).
Differential Via – Via-pair differential impedance through the plane clearance from a 2D field solution, antipad sizing for a target, stub resonance and delay.
Via Stitching & Via Fence Spacing – Stitching and fence via pitch from the wavelength (λ/10, λ/20), via-grid cell resonance, leakage between vias and plane-pair cavity resonances.
Interface Design Rules – Impedance, skew, loss budget and length limits of PCIe, USB, Ethernet, HDMI, DDR and other interfaces, applied to a layer of your own stackup with the field solver.

Stackup

Stackup Advisor – Find stackups by board thickness and layer count, with optional impedance requirements to rank candidates and solve trace widths.
Layer Stack Manager – 178 fab stackups from 2 to 12 layers, editable, with any signal layer sent to the impedance calculator.
PCB Laminate Materials (Dk / Df) – Datasheet Dk and Df of FR-4, low-loss and RF laminates (Isola, Panasonic, Rogers, Shengyi…) at any frequency, plus solder masks and copper foil roughness.

Thermal

Junction Temperature – Junction temperature from power and the thermal-resistance chain (θJA or θJC + θCS + θSA), and the maximum power for a Tj limit.
Thermal Via Array – Thermal resistance of a via array under a hot pad, with plugged or filled vias, and the temperature drop through the board.
Copper Area for Heat Spreading – How much copper a hot part needs: copper-pour thermal resistance by convection and radiation, junction temperature and the smallest pour for a Tj limit.

Power & conductors

Trace Width, Current & Temperature Rise – IPC-2221: width for a current, current for a width, or temperature rise of a trace, with resistance, voltage drop and loss.
Via Calculator – Via current capacity, resistance, thermal resistance, capacitance, inductance and rise-time impact.
Skin Effect & AC Resistance – Skin depth in copper and the AC resistance of a trace across frequency.
Fusing Current – Current that melts a trace in a given time (Onderdonk), for fault and surge analysis.
Wire Gauge & Voltage Drop – AWG diameter, area and resistance, cable voltage drop and loss, the smallest gauge for a drop limit, and Preece fusing current.
Conductor Spacing (IPC-2221) – Minimum electrical clearance between conductors from IPC-2221 Table 6-1: internal, external, coated, high altitude, assemblies.
Creepage & Clearance (IEC 60664-1) – Minimum clearance and creepage per IEC 60664-1: impulse voltage from mains and overvoltage category, pollution degree, CTI material group, reinforced insulation, altitude.

Power integrity

PDN Impedance Calculator – Target impedance, plane-pair capacitance, decoupling-capacitor resonance and the number of capacitors needed, with a log-log |Z|(f) plot.

Power supply

Power Tree Planner – Budget source and regulator currents across cascaded rails and loads, estimate losses, check ratings and record power-up dependencies.
Buck Converter Calculator – Buck power-stage sizing with conduction-mode checks, real inductor and capacitor ratings, IC timing limits and current waveforms across the input range.
Boost Converter Calculator – Boost power-stage sizing with conduction-mode checks, real inductor and capacitor ratings, IC timing limits and current waveforms across the input range.
LDO Regulator Power Dissipation – Linear regulator dissipation, junction temperature, efficiency and dropout headroom, with the maximum load for a Tj limit.
Feedback Resistor Divider – Standard-value R1/R2 for adjustable regulators: the best E12/E24/E96 pairs, output error, FB bias current and worst case with tolerance.

Components

Planar Spiral Inductor – Inductance of square, hexagonal, octagonal and circular PCB spirals (modified Wheeler and current-sheet models), with DC resistance and Q.
Through-Hole Padstack Calculator – Plated through-hole sizing per IPC-7251 / IPC-2221 / IPC-2222: hole, outer and inner pads, antipad, thermal relief and annular ring for levels A/B/C.
BGA Land Pattern – IPC-7351 land diameter for collapsing and non-collapsing BGA balls, with tolerance and courtyard, and escape-routing capacity between lands.
Resistor Color Code Calculator – Value, tolerance and temperature coefficient of 4-, 5- and 6-band resistors from their colours (IEC 60062), and the bands for any value.
SMD Resistor Code Calculator – Decode 3-digit, 4-digit and EIA-96 SMD resistor markings and R/m decimal notation, and find the code for any value.
Capacitor Code Calculator – Decode capacitor markings such as 104K and 2A473J: value, tolerance letter, voltage code, and dielectric codes such as X7R and C0G.

Electronics

Ohm's Law & Power – Enter any two of voltage, current, resistance and power to get the other two.
Reactance & LC Resonance – XL and XC at a frequency, LC resonance, the L or C for a target frequency, and series/parallel LC impedance with Q.
RC Low-Pass & High-Pass Filter Calculator – Passive RC low-pass and high-pass filters with source/load resistance, standard component selection, tolerance bounds and interactive gain and phase plots.
Crystal Load Capacitors & PPM – Crystal load capacitors with the nearest E12/E24 values and resulting CL, plus frequency error ↔ ppm and clock drift.
555 Timer Calculator – Astable frequency and duty cycle, resistor values for a target frequency, and monostable pulse width, from the TI NE555 equations.
I²C Pull-up Calculator – Pull-up resistor range for Standard, Fast and Fast-mode Plus I²C from bus capacitance, rise time and device sink current.
Logic-Level Compatibility Checker – Check worst-case VOH/VOL against VIH/VIL, static noise margins and receiver input-voltage limits.
ADC Input Settling Checker – Check source and RC filter settling into a SAR ADC sample capacitor during acquisition, with an optional filter-node recovery check.
Current-Sense Shunt Selector – Select a shunt from current range and voltage-drop budget, with power, tolerance, TCR and amplifier-offset checks.
Resistor Tools – Voltage divider with best E12/E24/E96 pairs, LED series resistor with power rating, and series/parallel R, C and L.
Attenuator Pads – Matched Pi, T and bridged-T pads with the nearest standard values, their actual loss and return loss, and resistor power.

Utilities

Projects – Save the inputs of every calculator for a board under one name, reopen them later, and export or import them as a project file.
Unit Converter – Length, copper weight, temperature, power (dBm/W/V) and frequency/wavelength.
Reference Charts – Drill sizes (number, letter, fractional, metric), ISO metric and Unified threads with tap and clearance drills, and the AWG wire table.