Boost converter duty cycle calculator
Stepping 5 V up to 12 V takes a duty cycle of about 0.5833 and gives a voltage gain of 2.4, and this calculator works out both from your two voltages. Any output that is not above the input is flagged. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Vin
- 5
- Vout
- 12
- V in
- 5
- Input voltage
- 5
- V out
- 12
- Output voltage
- 12
A boost converter duty cycle calculator turns the input and output voltages of a step-up switching regulator into the switch on-time fraction that ideal continuous-conduction-mode analysis predicts.
What boost duty cycle means for a step-up converter
A boost (step-up) DC–DC converter stores energy in an inductor while a power switch is on, then transfers that energy to the output capacitor and load when the switch turns off. In continuous conduction mode with an ideal switch, diode, and inductor, volt-second balance on the inductor over one switching period yields the classic voltage conversion law: Vout over Vin equals one divided by one minus D, where D is the fraction of the period the switch is closed.
Solving for duty gives the closed form D equals one minus Vin over Vout. Doubling Vout at fixed Vin raises D toward one; raising Vin toward Vout lowers D toward zero. Duty must stay strictly between zero and one exclusive for a finite boost gain: D equals zero is a direct short of the ideal model to Vout equals Vin, and D equals one would require infinite gain.
Classroom numbers are easy: Vin equals five and Vout equals twelve yields D equals one minus five twelfths, about zero point five eight three three, and gain two point four; Vin equals twelve and Vout equals twenty-four yields fifty percent duty and gain two. Teachers and automated graders care about the non-boost rejection as much as the arithmetic: a student who plugs Vout less than or equal to Vin has left the domain of the ideal boost formula, and a silent absolute-value fallback would hide that topology mistake.
Prefer consistent volt units for Vin and Vout so D is dimensionless and M is a pure voltage ratio.
Practical tips, limits, and related searches
Keep Vin and Vout inside the published absolute range so the ratio and complement stay finite under the magnitude cap. Remember that real converters need dead time, efficiency, and discontinuous-mode corrections: this tool reports the ideal CCM continuous duty only, so treat high-D results near ninety percent as a warning to re-check inductor current ripple and MOSFET stress rather than a magnetics design.
If you need efficiency-adjusted duty, apply D equals one minus eta times Vin over Vout by hand after the ideal result, or chain a separate loss model—this landing does not accept eta so goldens stay a pure two-field contract. This page targets people searching for a boost converter duty cycle calculator, step-up switching duty from Vin and Vout, or ideal CCM boost D online; it is not a buck calculator, not a PWM on-time from period tool, not an inductor current ripple designer, and not a full SPICE transient simulator.
Prefer this capability when you already have scalar input and output voltages and only need ideal D and M; if your source is a measured efficiency curve or discontinuous-mode boundary, convert those into an effective target Vout or duty first.
What you can do with it
Homework checks for ideal CCM boost duty
Students enter Vin and Vout from textbook boost problems and compare hand-written D, duty percent, and voltage gain against a deterministic result.
Pre-flight estimates for step-up rails
Designers estimate ideal switch duty from planned battery and regulated voltages before budgeting inductor, MOSFET, and diode stress.
FAQ
How is boost converter duty cycle calculated?
Duty percent is 100 · D. Keep Vin and Vout in the same voltage unit so D is dimensionless.
What happens when Vout is not greater than Vin?
A boost (step-up) stage requires Vout > Vin.
Does the calculator include efficiency or DCM?
No. It reports ideal CCM continuous duty only.
Is the boost converter duty cycle calculator free?
The browser tool is free and runs locally.
Why is a duty cycle near 90% a warning sign?
Because the result is the ideal value with no losses. When the duty cycle climbs that high, re-check the inductor ripple current and the stress on the switching transistor before trusting the design, since real converters behave differently at the extremes.
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/boost-duty \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"vin":5,"vout":12}'const res = await fetch("https://api.kit.forhosting.com/elec/boost-duty", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"vin": 5,
"vout": 12
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/boost-duty",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"vin": 5,
"vout": 12
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/boost-duty", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"vin":5,"vout":12}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"vin":5,"vout":12}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/boost-duty", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"vin": 5,
"vout": 12
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.boost_duty",
"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
Vout must be strictly greater than Vin: a buck or equal-voltage pair leaves the boost domain, so the API returns a clear invalid_input error instead of inventing a non-positive duty.
What boost duty cycle means for a step-up converter
The check path recomputes one over one minus D and compares it to Vout over Vin with the same fixed rounding used for published fields, so a successful response always ships with steps you can assert in tests or worksheets without floating-point ambiguity between the Worker and the browser.
How to call the API and what comes back
Both voltages must be strictly positive; values whose absolute magnitude is at or below one times ten to the minus fifteen are treated as non-positive and rejected. Prefer sending numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern including optional scientific notation. Send a JSON body with two required finite numbers: vin (aliases v_in, input_voltage, vin_v, v_source, and source_voltage) for the converter input in volts, and vout (aliases v_out, output_voltage, vout_v, v_load, and load_voltage) for the regulated output in volts. Absolute values must stay within the published limit of one trillion so intermediate ratios remain finite in IEEE double precision on the Worker and in the browser. Output must be strictly greater than input; equal or lower Vout is invalid_input for this boost-only model. On success the response echoes rounded vin, v_in, input_voltage, vout, v_out, and output_voltage; sets duty, duty_cycle, and duty_fraction to the same dimensionless fraction; duty_percent to one hundred times D; voltage_gain and conversion_ratio to Vout over Vin; voltage_gain_from_duty to one over one minus D as a consistency check; formula to the documented D and M strings; equation to a human-readable substitution line; unit labels for fraction, percent, volts, and V per V; message to a short English summary; and steps to an ordered array of given values, formulas, duty, percent, gain, check, and summary. Failed validation—missing fields, non-numeric strings, non-finite numbers, values outside absolute limits, non-positive Vin or Vout, or Vout not greater than Vin—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, limits, and related searches
When teaching, pair examples: five volts in and twelve volts out for a USB-boost-style rail; twelve volts in and twenty-four volts out for a clean fifty-percent case; and deliberately setting Vout equal to or below Vin to demonstrate the hard invalid_input path. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately set Vout less than Vin. Round-trip checks are easy: recompute one minus Vin over Vout and Vout over Vin by hand and confirm the published duty and voltage_gain match within the same twelve-decimal rounding, and confirm that scaling Vin and Vout by the same positive factor leaves D and M unchanged as the formula predicts.
Integration use cases
Unit tests for power-rail firmware and docs
Generate known-good boost duty and gain cases plus deliberate non-boost rejections for coding kata and datasheet-style expected values.
Technical questions
How is voltage gain related to duty cycle?
Ideal CCM boost obeys M = Vout/Vin = 1/(1 − D). Solving for D recovers D = 1 − Vin/Vout. This tool returns both M and the 1/(1 − D) check.