BlueJoule composes measured activity energy, a chip, and a battery into a battery-life estimate and a brown-out check. It labels every input measured or estimated, so you get a number you can defend instead of one you have to trust.
Pick a chip, pick a battery, and add the activities your firmware actually runs: advertising, a notification, a sensor read, each at its real rate. BlueJoule returns a battery-life band and a brown-out verdict. A non-connectable beacon on an nRF54L15 and a CR2032 looks like 2.3 to 2.9 years at 7.78 µA average. Healthy, on paper. But the calculator flags that the radio’s current burst sags the coin cell past the chip’s brown-out threshold near end of life. The average current would never have told you that.
| Activity | Rate | Per | µA |
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Measured versus estimated. Every input carries where it came from. A card is labeled by how its number was produced: measured on the bench, or an estimate. When your result mixes measured and estimated inputs, the tool says so on the result itself, it never rolls an estimate up into a number that looks fully measured. You always know which parts of your battery-life number are real bench data and which are a model.
The brown-out check. A battery-life average can look excellent while the product still dies in the field. A small or aging cell sags under the radio’s burst, and if it drops below the chip’s brown-out threshold, the device resets. BlueJoule checks whether your worst burst pushes your cell past that threshold near end of life. That deliverability check is the honesty an energy-only score cannot express.
An energy number does not exist in the abstract. It is bound to a specific platform: a chip, its memory configuration, its regulator, and the supply voltage it runs at, and the regulator changes how it behaves. On a buck-regulated chip like the nRF54L15, the current the chip pulls from the cell climbs as the battery sags toward end of life, which is exactly what pushes a weak cell toward brown-out. So BlueJoule binds the hardware first and measures, instead of estimating from a datasheet. When a number here says “measured,” it means a real board, a real supply, on the bench.
Each behavior your firmware runs is a card: the energy of one activity (a non-connectable advertisement, a notification, a connection event) on one hardware platform, labeled measured or estimated and carrying the conditions behind it. The calculator composes those activity cards, the platform’s sleep floor, and your battery into the final battery-life band and brown-out verdict. Swap the battery or change a rate, and it recomposes.
The cards here are measured on reference hardware, so you can explore the tradeoffs for free before you commit to a design. A real product’s number comes from your own platform, your chip, your firmware build, your battery, measured. We would rather show you a clearly labeled estimate than hand you a number that looks measured and is not.
BlueJoule is an open, vendor-neutral benchmark for Bluetooth LE energy, created by Bob Frankel and stewarded by The EM Foundation. The workload and the methodology are published, and the benchmark is free to run. The calculator on this page is how you put those numbers to work on a real product.
Pick your chip, your battery, and your activity mix above, and get a battery-life band with an honest brown-out check in under a minute.