Bench Tools
Electronics calculators that get out of your way
Eight fast, accurate tools for the things you look up constantly at the bench — resistor bands, SMD markings, Ohm's law, LED droppers, dividers, capacitor codes and trace widths. Everything runs locally in your browser. Nothing you type is sent anywhere.
Why another set of calculators?
Most component calculators on the web are slow, buried under interstitials, or wrong in the edge cases that actually matter — the 6-band resistor with a temperature coefficient, the EIA-96 marking that looks like a 3-digit code, the divider that sags because you picked megohms next to a 10 kΩ load. These tools are built to be correct in those corners and to load in well under a second on a phone in a workshop with two bars of signal.
Everything is bidirectional where that makes sense
The resistor colour code calculator works in both directions: read the bands off a part you're holding, or tell it the value you need and it shows you which bands to look for in the drawer. The Ohm's law calculator takes any two of voltage, current, resistance and power and returns the other two. The divider calculator will solve for output voltage or work backwards to a resistor pair built from real E-series parts.
Real parts, not ideal ones
A calculator that tells you to fit a 3,142 Ω resistor has not finished the job. Wherever a result implies a physical component, these tools also give you the nearest value in the E-series you're actually buying from, the error that substitution introduces, and the power the part will dissipate so you can pick a package that survives.
No accounts, no stored data
There is no login, no saved history and no analytics on what you calculate. Every computation happens in JavaScript in your own browser — you can pull the network cable out and the tools keep working. The site is supported by advertising, which is disclosed in the privacy policy.
Quick reference: resistor colour bands
The chart every one of these tools is built on. Digit bands run black through white for 0–9; the multiplier band uses the same sequence as powers of ten, extended with gold and silver for the fractional multipliers.
| Colour | Digit | Multiplier | Tolerance | Temp. coeff. |
|---|---|---|---|---|
| Black | 0 | ×1 | — | — |
| Brown | 1 | ×10 | ±1% | 100 ppm/°C |
| Red | 2 | ×100 | ±2% | 50 ppm/°C |
| Orange | 3 | ×1 k | — | 15 ppm/°C |
| Yellow | 4 | ×10 k | — | 25 ppm/°C |
| Green | 5 | ×100 k | ±0.5% | — |
| Blue | 6 | ×1 M | ±0.25% | 10 ppm/°C |
| Violet | 7 | ×10 M | ±0.1% | 5 ppm/°C |
| Grey | 8 | ×100 M | ±0.05% | — |
| White | 9 | ×1 G | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
Open the interactive resistor colour code calculator to apply this chart to a specific part, including 5- and 6-band precision resistors.