Linear regulator power calculator
Stepping 12 V down to 5 V at 0.5 A turns 3.5 W into heat: enter input, output and load current to see the regulator's dissipation, the power that reaches the load and the approximate efficiency, before you pick a heat sink. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Input voltage
- 12
- Output voltage
- 5
- Load current
- 0.5
- Voltage drop
- 7
- Power watts
- 3.5
- Load power watts
- 2.5
- Input power watts
- 6
Linear regulators turn excess headroom into heat. Whenever a series pass element holds a fixed output below a higher input rail, the product of the voltage drop and the load current becomes continuous package dissipation that must leave through the die, the tab, the board copper, or an external heat sink. This linear regulator power calculator accepts the three numbers every datasheet and schematic already state—input voltage Vin, regulated output Vout, and load current Iload—applies the textbook identity Pd equals Vin minus Vout times Iload, and returns dissipation in watts together with voltage drop, load power, input power, and the approximate efficiency Vout over Vin.
Why linear regulators dissipate (Vin − Vout) · Iload
In a classic series linear regulator the pass device sits between the unregulated input and the regulated output and acts as a controlled resistor that continuously adjusts so Vout stays at the setpoint. Kirchhoff’s voltage law says the voltage across that pass element is Vin minus Vout, and the current through it is essentially the load current when ground-pin or quiescent current is small compared with the load.
Instantaneous power in a two-terminal device is voltage times current, so package dissipation simplifies to Pd equals open parenthesis Vin minus Vout close parenthesis times Iload. That heat is not optional: every watt of dissipation must leave the silicon through the package thermal path, and if junction temperature rises too far the regulator folds back, drifts, or shuts down. The same numbers also yield load power Vout times Iload and, neglecting ground current, input power Vin times Iload, so efficiency is approximately Vout over Vin expressed as a percent.
A twelve-volt rail stepped down to five volts at half an ampere therefore dumps three and a half watts as heat while delivering only two and a half watts to the load, which is why high drop at high current is a heat-sink problem rather than a resistor-value problem.
Where linear regulator power calculators earn their keep
Introductory power electronics labs constantly assign a twelve-volt supply, a five-volt or three-point-three-volt regulator, and a stated load current so students can compute package dissipation before they pick a TO-220 heat sink or decide the part must become a switcher. Firmware and hardware bring-up teams size intermediate rails for sensors, radios, and microcontrollers from a higher industrial bus, then record Pd and approximate efficiency in the thermal section of the design review.
Repair technicians reconstructing a failed linear stage from a scorched package often only know the marked Vout, the measured Vin, and the approximate load; a trusted wattage estimate avoids restuffing another undersized part without copper or a clip-on sink. Keep parallel resistance, voltage-divider, LED series resistor, and zener dropper landings separate so each search intent has one clear page rather than a overloaded multi-topology tool that confuses both students and search engines.
What you can do with it
Heat sink and package selection
Compute Pd from Vin, Vout, and Iload before choosing a TO-220 sink, board copper, or a switcher when linear drop would overheat the package.
FAQ
How do I calculate linear regulator power dissipation?
Send positive Vin, Vout, and load current in amperes with Vout strictly less than Vin.
Why must Vout be less than Vin?
A series linear regulator can only drop voltage.
Does the calculator include quiescent or ground-pin current?
No. This first-pass model uses Pd = (Vin − Vout) · Iload and η ≈ Vout/Vin, neglecting ground-pin current. For precision thermal work add Vin · Iq from the datasheet after this estimate.
What units should I use for load current?
Amperes. Convert milliamps first: 500 mA is 0.5 A. Non-positive or non-finite currents fail validation and are not billed.
How much heat does a 12 V to 5 V regulator make at 0.5 A?
3.5 W. The 7 V dropped across the regulator times 0.5 A becomes heat, while the load receives only 2.5 W. That is a heat-sink problem, and a sign that a switching converter may suit the design better.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/elec/linear-regulator-power \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"input_voltage":12,"output_voltage":5,"load_current":0.5}'const res = await fetch("https://api.kit.forhosting.com/elec/linear-regulator-power", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"input_voltage": 12,
"output_voltage": 5,
"load_current": 0.5
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/linear-regulator-power",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"input_voltage": 12,
"output_voltage": 5,
"load_current": 0.5
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/linear-regulator-power", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"input_voltage":12,"output_voltage":5,"load_current":0.5}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"input_voltage":12,"output_voltage":5,"load_current":0.5}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/linear-regulator-power", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"input_voltage": 12,
"output_voltage": 5,
"load_current": 0.5
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.linear_regulator_power",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
When the output equals or exceeds the input there is no valid linear headroom and the request fails with invalid_input instead of a zero or negative absurdity.
Input contract, response shape, and error behaviour
Example values that match a common wall-wart to logic rail design are input twelve, output five, and load current zero point five. If you need series LED current limiters, shunt zener dropper resistors, switching converter efficiency models with duty cycle, or full theta-JA junction temperature solvers, treat those as separate tools rather than overloading this three-input linear dissipation page. POST a JSON body with three required finite positive numbers: input_voltage in volts for the unregulated or upstream rail, output_voltage in volts for the regulated setpoint, and load_current in amperes for the continuous current drawn from the output. Aliases such as vin, v_in, vs, supply_voltage, vout, v_out, vo, i_load, il, current, and i_out are accepted so form widgets and scripts stay convenient, but only one key may appear for each quantity. Missing fields, non-numeric strings, NaN, Infinity, non-positive values, and any case where the output voltage is greater than or equal to the input fail with invalid_input and are not charged. On success the response echoes the cleaned inputs, voltage_drop as Vin minus Vout, power_watts as the package dissipation Pd, load_power_watts as Vout times Iload, input_power_watts as Vin times Iload, efficiency_percent as one hundred times Vout over Vin, unit_power watt, method linear_regulator_dissipation, and the formula string restating Pd and approximate efficiency. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where linear regulator power calculators earn their keep
Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.
Integration use cases
Lab homework and design reviews
Let students and reviewers verify dissipation and approximate efficiency for textbook linear regulator problems with deterministic golden answers.
Thermal tables in CI fixtures
Script the same Pd formula used in the browser so automated fixtures assert that stocked regulators still meet wattage limits at max load.
Technical questions
What does the linear regulator power calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.