Colour bands to resistance
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.
api.oanor.com/resistor-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 77 ms
- Server probes · 24h
- Subscribers
- 4,743
- active
- Total calls
- 76
- last 7 days
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
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
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
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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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
Newegg API
Live product search from Newegg.com, the major electronics & tech retailer. Search any keyword — laptop, rtx 4070, ssd — and get the product listings with title, brand, model, current price, original price, image, rating, review count, in-stock status, seller and the Newegg product URL. Prices are live USD. Ideal for shopping, price-comparison, deal-tracking and e-commerce dashboards.
api.oanor.com/newegg-api
RTD Pt100 Sensor API
RTD (resistance-temperature-detector) sensor maths as an API, computed locally and deterministically with the IEC 60751 Callendar–Van Dusen equation — the resistance, temperature and tolerance numbers an instrumentation or controls engineer reads a Pt100 or Pt1000 with. The resistance endpoint gives the sensor resistance from temperature: above 0 °C, R = R₀·(1 + A·T + B·T²) with A = 3.9083×10⁻³ and B = −5.775×10⁻⁷; below 0 °C a third term adds C·(T−100)·T³ — a standard Pt100 (100 Ω at 0 °C) reads 138.51 Ω at 100 °C and 80.31 Ω at −50 °C, and a Pt1000 is ten times that. The temperature endpoint inverts it to turn a measured resistance back into temperature — analytically above 0 °C, iteratively below — exactly what a transmitter does with the bridge reading, and a reminder that a 3- or 4-wire connection cancels the lead-wire resistance so it does not read as extra degrees. The tolerance endpoint gives the IEC 60751 accuracy band in both °C and Ω by class — AA ±(0.10 + 0.0017·|T|), A ±(0.15 + 0.002·|T|), B ±(0.30 + 0.005·|T|), C ±(0.60 + 0.010·|T|) — the error growing with distance from 0 °C. Everything is computed locally and deterministically, so it is instant and private. Ideal for instrumentation and controls software, data-logger and transmitter firmware, calibration and industrial-IoT tools. Pure local computation — no key, no third-party service, instant. 3 compute endpoints. For NTC thermistors use a thermistor API; for thermocouples a thermocouple API.
api.oanor.com/rtd-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())Ratings
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