Power Budget Calculator

It calculates total system current draw (in mA), total power consumption (in mW and W), and recommends minimum power supply current rating and backup battery capacity (in mAh) based on desired runtime. The tool assumes continuous operation and uses Ohm’s Law (P = V × I) for DC power estimation.

Use it early in the schematic and PCB design phase—after component selection but before finalizing the power supply or battery. It’s especially valuable for battery-powered IoT nodes, sensor gateways, portable instrumentation, and low-power embedded systems where energy efficiency is critical.

Each field accepts the *maximum typical* current draw (in mA) of that subsystem under active operation. For components with variable duty cycles (e.g., wireless radios), enter peak current during transmission—not average—so the power supply can handle worst-case load without brownout.

Typical values: MCU (1–100 mA, depending on clock speed & peripherals), sensors (0.1–20 mA), Bluetooth/WiFi modules (10–250 mA TX peak), LEDs (5–30 mA each), and LDOs/regulators (add 1–5 mA quiescent current separately). Always verify with datasheets—low-power modes can reduce MCU current to <1 µA, but this tool targets active-state budgeting.

It assumes a single primary supply rail powering all listed subsystems (e.g., 3.3 V for most modern MCUs and peripherals). If your design uses multiple rails (e.g., 5 V for motors, 3.3 V for logic), calculate each rail separately and sum total power. This tool is optimized for unified low-voltage digital systems.

This calculator estimates *worst-case continuous* power draw. To estimate average current for duty-cycled systems, manually weight each subsystem’s current by its duty cycle (e.g., MCU @ 50 mA for 1% of time → 0.5 mA avg). For accurate battery life, combine this tool’s peak result with a separate duty-cycle analysis.

Double-check that inputs reflect actual *peak* currents—not average or idle values—and confirm all subsystems operate simultaneously. Also verify supply voltage matches your regulator output (e.g., 3.3 V, not battery voltage). Overestimating wireless TX or LED current is the most common cause of inflated results.

Yes—it computes required battery capacity (mAh) based on total system current and your specified runtime (assumed in hours). Remember to apply a derating factor (e.g., 20–30%) for battery aging, temperature effects, and inefficiencies in voltage regulation or charging circuits.

No—it calculates *load-side* power only. To size the input power source (e.g., wall adapter or battery), increase the recommended supply current by 10–25% to account for regulator dropout, switching losses, or linear regulator thermal dissipation, depending on your chosen topology.

This tool focuses on *system-level power provisioning*: ensuring the supply can deliver sufficient current and voltage under load. A battery life estimator typically starts from capacity and duty cycle to predict runtime. Use both—this one first to validate feasibility, then a life estimator for optimization.