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API · /resistor-api

Resistor Color Code API

healthy 4,743 Subscribers

Read and write resistor colour codes and snap values to the standard E-series. The decode endpoint takes the colour bands of a 3-, 4-, 5- or 6-band resistor and returns the resistance in ohms (nicely formatted as Ω/kΩ/MΩ/GΩ), the significant digits and multiplier, the tolerance, the minimum and maximum resistance that tolerance implies, and — for 6-band parts — the temperature coefficient in ppm/K. The encode endpoint goes the other way: give it a resistance in ohms (and optionally a band count and tolerance) and it returns the colour bands, picking the nearest value representable with the available significant digits. The eseries endpoint snaps any value to the nearest preferred resistor value in the E6, E12, E24, E48 or E96 series and reports the percentage error and the neighbouring preferred values. It uses the standard IEC 60062 colour assignments (including gold ×0.1 and silver ×0.01 multipliers and the implicit ±20% of a 3-band part). Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics design, PCB and BOM work, lab and hobby bench use, repair and reverse-engineering, and teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is for resistor colour codes; for general number formatting use a number-format API.

#resistor #color-code #electronics #e-series #eda #developer-tools
api.oanor.com/resistor-api
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/api/resistor-api/openapi.json
/api/resistor-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
85 ms
Server probes · 24h
Subscribers
4,743
active
Total calls
40
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 5,735 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 5,735 calls/month
  • 2 req/sec
  • Decode + encode + E-series
  • No credit card
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Starter

€7.25 /month

  • 15,250 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 15.25k calls/month
  • 8 req/sec
  • 3/4/5/6-band + tempco
  • Email support
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Pro

€27.15 /month

  • 203,500 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 203.5k calls/month
  • 20 req/sec
  • EDA / BOM / bench pipelines
  • Priority support
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Mega

€65.15 /month

  • 1,060,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 1.06M calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Voltage Divider API

Resistive voltage-divider circuit design as an API, computed locally and deterministically. The divide endpoint takes an input voltage and two resistors and returns the output voltage Vout = Vin·R2/(R1+R2), the current I = Vin/(R1+R2) that flows through the chain, and the power dissipated in each resistor and in total — a 12 V source with R1 = 1 kΩ and R2 = 2 kΩ gives 8 V at 4 mA. The loaded endpoint adds a load resistor across R2, computes the parallel combination R2′ = R2·RL/(R2+RL) and the loaded output Vout = Vin·R2′/(R1+R2′), and reports the droop in volts and percent against the unloaded value, the classic mistake when a divider feeds a real load. The resistor endpoint sizes the missing resistor for a target output — R2 = R1·Vout/(Vin−Vout) or R1 = R2·(Vin−Vout)/Vout — so you can pick parts for a reference or sensor-bias point. All quantities are volts, ohms, amps and watts. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, embedded, hardware, sensor-interfacing and EE-education app developers, reference-voltage and bias-network tools, and maker software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the resistive divider; for a single Ohm’s-law relationship use an Ohm’s-law API and for RC/RL filters an RC-filter API.

api.oanor.com/voltagedivider-api

LED Resistor API

LED current-limiting-resistor maths as an API, computed locally and deterministically. The resistor endpoint sizes the series resistor for a single LED, R = (V_supply − V_forward) / I, and returns the resistor power dissipation (I²·R), the LED power, a recommended resistor wattage rating and the nearest E12 standard value (rounded up so the LED current stays at or below the target). The series endpoint sizes the one shared resistor for several LEDs wired in series, where the forward voltages add, R = (V_supply − n·V_f) / I, and flags when the supply is too low for the string. The parallel endpoint gives the per-LED resistor for LEDs in parallel (each needs its own) and the total current the supply must deliver. Currents are entered in milliamps. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, maker, Arduino and hardware app developers, LED and lighting-circuit design tools, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is LED resistor sizing; for general Ohm's law and reactance use an Ohm's-law API and for AWG wire properties use a wire-gauge API.

api.oanor.com/ledresistor-api

RC Filter API

First-order RC and RL passive-filter design as an API, computed locally and deterministically. The lowpass and highpass endpoints take a resistor and capacitor (RC) or a resistor and inductor (RL) and return the −3 dB cutoff frequency (fc = 1/(2πRC) for RC, R/(2πL) for RL), the time constant (τ = RC or L/R) and the angular cutoff; pass a frequency as well and they add the magnitude response as a linear gain and in decibels and the phase shift in degrees — a 1 kΩ / 1 µF low-pass has fc ≈ 159.15 Hz, and right at the cutoff the gain is −3.01 dB with −45° phase for a low-pass or +45° for a high-pass. The component endpoint solves the missing one of fc, R and C from the other two (fc = 1/(2πRC)), so you can size a resistor or capacitor for a target cutoff. All quantities are SI: ohms, farads, henries and hertz. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, audio, embedded, signal-processing and EE-education app developers, filter-design and circuit-sizing tools, and maker software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is first-order single-pole filter design; for full RLC impedance and resonance use an impedance API and for stored capacitor energy a capacitor API.

api.oanor.com/rcfilter-api

Chebyshev Filter API

Chebyshev Type I filter-design maths as an API, computed locally and deterministically. The order endpoint computes the minimum filter order to meet a specification, n = ⌈acosh(√((10^(As/10)−1)/(10^(Ap/10)−1))) / acosh(fs/fp)⌉, from the passband edge frequency and its ripple and the stopband edge and its required attenuation — a Chebyshev filter usually needs a lower order than a Butterworth for the same specification, trading a flat passband for equiripple. The response endpoint computes the equiripple magnitude response, |H| = 1/√(1 + ε²·Tₙ²(f/fc)) with the ripple factor ε = √(10^(Ap/10) − 1) and the Chebyshev polynomial Tₙ, in linear and decibel form — in the passband the magnitude ripples between 0 and −Ap dB and reaches exactly −Ap dB at the cutoff, then rolls off faster than a Butterworth. The ripple endpoint converts between the passband ripple in decibels and the ripple factor ε, with the passband maximum and minimum. Frequencies are in hertz, ripple and attenuation in decibels and the order a positive integer. Everything is computed locally and deterministically, so it is instant and private. Ideal for DSP, audio, RF, communications and instrumentation app developers, filter-design and selectivity tools, and signal-processing education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the Chebyshev Type I filter; for the maximally-flat Butterworth use a Butterworth API.

api.oanor.com/chebyshev-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Resistor Color Code API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Resistor Color Code API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Resistor Color Code API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Resistor Color Code API cost?
Resistor Color Code API has a free tier with 100 calls / month. Paid plans start at €7.25 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Resistor Color Code API GDPR-compliant?
All requests to Resistor Color Code API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/resistor-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/resistor-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/resistor-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/resistor-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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