Resistor Calculator
Fast, accurate, and free online Resistor Calculator tool that runs directly in your browser.
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| # | R | Unit | |
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Other tools you may find usefulResistor calculator - barcodes, SMD, tolerance and E12/E24 series
Decipher the resistor value from color bars or SMD code, convert Ω–kΩ–MΩ units, check tolerance, multiplier and temperature coefficient. Built-in E6, E12 and E24 preference series make it easy to select the closest catalog value. Additional sections help you quickly calculate series and parallel connections and power losses.
Run the resistor calculator See color legend and examples
What the calculator calculates
- Resistor valuefrom strips 3–6: significant figures, multiplier, tolerance, possibleppm/°C.
- SMD valuefrom 3-/4-digit code and EIA-96 (code + multiplier letter).
- Konwersjeunit conversions: Ω ↔ kΩ ↔ MΩ rounded to the E6/E12/E24 series.
- Connectionsseries and parallel connections: equivalent resistance for several elements.
- Power dissipationacross the resistor at a given voltage or current.
How to read resistor strips
3 and 4 strips
Strips 1-2are significant digits,strip 3is the multiplier,strip 4- tolerance.
5 and 6 bars
The first three bars are significant digits, the fourth - multiplier, the fifth - tolerance, the sixth -ppm/°C.
Color and Tolerance Legend
| Color | Digit | Multiplier | Tolerance | PPM/°C |
|---|---|---|---|---|
| Black | 0 | ×10⁰ | – | – |
| Brown | 1 | ×10¹ | ±1% | 100 ppm |
| Red | 2 | ×10² | ±2% | 50 ppm |
| Orange | 3 | ×10³ | – | 15 ppm |
| Yellow | 4 | ×10⁴ | – | 25 ppm |
| Green | 5 | ×10⁵ | ±0.5% | – |
| Blue | 6 | ×10⁶ | ±0.25% | 10 ppm |
| Purple | 7 | ×10⁷ | ±0.1% | 5 ppm |
| Gray | 8 | ×10⁸ | ±0.05% | 1 ppm |
| White | 9 | ×10⁹ | – | – |
| Gold | – | ×10⁻¹ | ±5% | – |
| Silver | – | ×10⁻² | ±10% | – |
| Without strap | – | – | ±20% | – |
SMD codes: 3-, 4-digit and EIA-96
3-/4-digit codes
The last digit is the number of zeros. 472 ⇒ 47 × 10² = 4.7 kΩ. 1001 ⇒ 100 × 10¹ = 1 kΩ.
EIA-96 codes
Two digits (value from table 01–96) and the multiplier letter: Y=×10⁻², R=×10⁻³, A=×10⁻¹, B=×10⁰, C=×10¹, D=×10² etc.
Formulas and quick conversions
Preferential series E6/E12/E24
Preferential series distribute values logarithmically in each decade, which facilitates selection with tolerance. For example, E12 has 12 values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 (multiplied by 10ⁿ).
| Series | Number of values/decade | Sample string | Typical tolerance |
|---|---|---|---|
| E6 | 6 | 10, 15, 22, 33, 47, 68 | ±20% |
| E12 | 12 | 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 | ±10% |
| E24 | 24 | 10, 10.5, 11, 11.5, … 91, 95 | ±5% |
Practical examples
4 bars: 1 kΩ ±5%
Brown – Black – Red – Gold ⇒ 1 kΩ in the range of 950–1050 Ω.
Selection of the nearest E24: 1.0 kΩ sought without corrections.
SMD 103
103 ⇒ 10 × 10³ = 10 kΩ. Assuming ±1%, the range is 9.9–10.1 kΩ.
EIA-96: 24B
Code 24 ⇒ 178, letter B ⇒ ×10⁰. Result ≈ 178 Ω.
Voltage divider
You want half the voltage: choose R₁ = R₂, e.g. 10 kΩ and 10 kΩ with E24. Take the load into account in the design.
Resistor power and thermal safety
- Check the catalog power: 0.063 W, 0.125 W, 0.25 W, 0.5 W, 1 W, 2 W etc.
- Calculate the power loss: P = U²/R or I²R and add a margin of 50-100%.
- For high voltages, include spacing and component breakdown voltage.
Resistor calculator - bar code in practice
The resistor calculator is most often used to read a bar code: in the4-bar versionthe first two bars are significant digits, the third is the multiplier, and the fourth is the tolerance; in the5-bar version(precision resistors), there are three significant digits. We read the resistor from the side of the strips pushed closer to the edge - the tolerance strip (usually gold or silver) is always the last one.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1 k | — |
| Yellow | 4 | ×10 k | — |
| Green | 5 | ×100 k | ±0.5% |
| Blue | 6 | ×1 M | ±0.25% |
| Purple | 7 | ×10 M | ±0.1% |
| Gray | 8 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Example:stripes yellow–purple–red–goldis 4 and 7 (significant digits) × 100 =4700 Ω = 4.7 kΩ ±5%. The same resistor in the 5-strip version would have yellow–purple–black–brown–brown stripes (470 × 10 = 4.7 kΩ ±1%).
Connecting resistors: series and parallel
When you don't have the value you need on hand, you can combine it with several resistors. Whenis connected in seriesthe resistances simply add up: R = R1 + R2 + … - two 2.2 kΩ resistors give 4.4 kΩ. Inparallel connectionthe reciprocals add up: 1/R = 1/R1 + 1/R2 + ..., and for two resistors a convenient formula is R = (R1 × R2) / (R1 + R2) - two parallel 10 kΩ resistors give 5 kΩ, and the resultant is always smaller than the smallest of them. The resistor calculator on this page allows you to quickly check both configurations without manually counting fractions.
FAQ
I don't see the sixth bar. Is this an error?
No. The sixth band (ppm/°C) is mainly found in precision metal film resistors. Typical pieces have 4-5 stripes.
What is the difference between E12 and E24?
E24 contains denser values between decades, which facilitates a more accurate match. Typical tolerance for E24 is ±5%, E12 ±10%.
How to convert SMD code 0R, 00, 000?
These are jumpers with virtually zero resistance. In design, treat it as a conductive connection.
How to select the resistor power?
Calculate P and select an element with a margin of at least ×1.5. For impulses, use an even larger margin.
Resistor Connections - Quick Summary
Serial
You add values. The current is the same, the voltages are divided in proportion to the resistance.
Parallel
You add the inverses. The voltage is the same, the currents add up.
Summary:The resistor calculator instantly decodes color bars and SMD codes, provides tolerance, multiplier, ppm/°C and converts units. The E6/E12/E24 series help you select a real value from the catalog, and the connection and power modules allow you to complete the project without additional calculations.
Check resistor value Select from E12/E24 series