| Battery Energy | — |
| Usable Energy | — |
| Load Power | — |
| Runtime (hours) | — |
| Runtime (mins) | — |
| Capacity Used / hr | — |
| Light use (50% load) | — |
| Normal use (100%) | — |
| Heavy use (150%) | — |
| Device | Typical Capacity |
| Budget Android phone | 3000–4000 mAh / 3.7 V |
| Flagship smartphone | 4500–5000 mAh / 3.87 V |
| iPad / Android tablet | 7000–10000 mAh / 3.7–3.8 V |
| Laptop (mid-range) | 45–60 Wh / 11.1–15.4 V |
| Laptop (premium) | 80–100 Wh / 15.4 V |
| 10 000 mAh power bank | 10000 mAh / 3.7 V = 37 Wh |
| AA battery (alkaline) | 2400–3000 mAh / 1.5 V |
| 18650 Li-ion cell | 2200–3500 mAh / 3.6 V |
| 12 V car battery (AGM) | 50–100 Ah / 12 V = 600–1200 Wh |
| E-bike battery (48 V) | 10–20 Ah / 48 V = 480–960 Wh |
| Total load | — |
| Battery energy (Wh) | — |
| Runtime estimate | — |
| Bluetooth (active) | 30–100 mW |
| Wi-Fi (active) | 150–400 mW |
| 4G LTE (streaming) | 500–1000 mW |
| GPS receiver | 50–250 mW |
| Phone screen (mid) | 400–700 mW |
| Laptop screen | 3–10 W |
| CPU (idle) | 1–5 W |
| CPU (load) | 10–45 W |
| IoT microcontroller | 5–50 mW |
| Arduino (active) | 150–250 mW |
| Charge power | — |
| mAh to fill | — |
| Time (CC phase) | — |
| Total time (CC+CV) | — |
| Energy added (Wh) | — |
| Standard USB (5W) | ~3–4 hrs |
| Quick Charge 3.0 | ~1.5–2 hrs |
| 25 W fast charge | ~1–1.5 hrs |
| 65 W GaN charger | ~45–60 min |
| 120 W super-fast | ~20–30 min |
Times are for a 4000 mAh phone battery from 0%. Actual times vary by charger protocol, cable quality, and device temperature.
| Health | — |
| Lost capacity | — |
| Cycles until 80% | — |
| Est. cycles left | — |
| Battery Type | Typical Cycles |
| Lithium-ion (Li-ion) | 300–500 cycles to 80% |
| LiFePO4 | 2000–5000 cycles to 80% |
| Lead-acid | 200–300 deep cycles |
| NiMH | 500–1000 cycles |
| Solid-state (new) | 1000+ cycles |
| Effective panel output | — |
| Net charge per day | — |
| Days to full | — |
| Hours of sun needed | — |
| Tropical / Desert | 5.5–7 hrs/day |
| Southern US / India | 4.5–6 hrs/day |
| Central Europe / UK | 2.5–4 hrs/day |
| Northern Europe | 1.5–3 hrs/day |
| Winter (high lat.) | 0.5–2 hrs/day |
Peak sun hours are not the same as hours of daylight — they represent hours of equivalent full-sun irradiance (1000 W/m²).
Use an MPPT charge controller instead of a basic PWM controller — MPPT can improve efficiency by 20–30% in partially shaded or cold conditions.
Angle your panel at your latitude for best year-round performance. Tilt it more steeply in winter to capture the lower sun angle.
Panel wattage ratings are measured at STC (Standard Test Conditions: 25 °C, full sun). Real output is typically 75–90% of rated watts.
| Battery energy (Wh) | — |
| Grid energy drawn (Wh) | — |
| Cost per charge | — |
| Cost per day | — |
| Cost per month | — |
| Cost per year | — |
| Annual kWh used | — |
| USA (avg.) | ~$0.12–0.16/kWh |
| UK | ~£0.24–0.28/kWh |
| Germany | ~€0.30–0.38/kWh |
| India | ~₹6–9/kWh |
| Australia | ~A$0.25–0.35/kWh |
| Canada | ~C$0.10–0.17/kWh |
| France | ~€0.20–0.25/kWh |
Rates vary by region and time of use. Check your electricity bill for exact figures.
| Application | Typical Discharge C-Rate |
| Smartphone (screen on) | 0.2C–0.5C |
| Laptop (light use) | 0.2C–0.4C |
| Laptop (gaming/render) | 0.5C–1.0C |
| RC car / hobby motor | 20C–50C burst |
| FPV drone (race) | 30C–100C burst |
| Power tool (drill) | 5C–15C |
| Electric vehicle (cruise) | 0.5C–1C |
| EV (peak acceleration) | 3C–5C |
| Grid storage (ESS) | 0.1C–0.5C |
| UPS / standby | 0.05C–0.2C |
| Configuration | — |
| Total cells | — |
| Pack voltage | — |
| Pack capacity | — |
| Pack energy (Wh) | — |
| Max continuous current | — |
| Max peak power | — |
| Pack internal resistance | — |
Series (S): Adds voltage, keeps capacity the same. 3S × 3.7 V = 11.1 V, still 3000 mAh per parallel group.
Parallel (P): Keeps voltage the same, multiplies capacity. 2P × 3000 mAh = 6000 mAh, still 3.7 V per series group.
Combined (e.g. 3S2P): Voltage × series cells, capacity × parallel cells. 3S2P gives 11.1 V at 6000 mAh = 66.6 Wh.
Always use cells of the same make, model, and charge level when building packs to avoid imbalance and safety risks.
Enter values above to see safety warnings.
| Metric | A | B | C |
| Enter battery data above to compare. | |||
Find exactly how long your battery lasts. Enter mAh, voltage, and device load to get runtime in hours. Also converts Wh, estimates charge time, checks battery health, and plans solar charging — all in one free tool.
Eight purpose-built tools to cover every battery question — from quick runtime checks to full solar power planning.
Enter capacity in mAh, nominal voltage, and device load in milliamps or watts. Get runtime in hours and minutes with a real-world efficiency factor built in. Covers phones, laptops, power banks, IoT sensors, EV packs, and more.
Convert freely between watt-hours and milliamp-hours at any voltage. Also outputs joules, kWh, and amp-hours. Includes a reference table of real battery capacities for phones, laptops, power banks, 18650 cells, e-bike packs, and car batteries.
Add individual components — screen, CPU, Wi-Fi, GPS, sensors — and input their wattage. The tool sums total load and calculates how long your battery lasts under that combined draw. Presets for phone idle, phone active, laptop idle, laptop under load, IoT device, and LED strip.
Know exactly how long charging takes based on battery size and charger current. Covers both the fast CC phase and the slower CV top-up phase (×1.2 factor). Supports partial charging — enter current battery level to calculate time from any starting point, not just from flat.
Compare original rated mAh against current measured capacity to see health as a percentage. Enter charge cycle count and battery chemistry (Li-ion, LiFePO4, Lead-acid, NiMH) to estimate remaining cycles before the standard 80% replacement threshold.
Calculate how many days a solar panel takes to fully charge a battery. Enter panel wattage, average peak sun hours for your region, system efficiency, and any simultaneous load — the tool computes net daily charge and total time to full. Region reference table included.
One-click presets for the most common scenarios: smartphone, tablet, laptop, power bank, IoT sensor, and EV pack on the runtime tab; standard USB 5 W, 18 W fast charge, 25 W, 65 W GaN, and 100 W on the charge time tab. Presets fill all fields instantly so you can calculate in seconds.
See three runtime estimates side by side for the same battery: light use at 50% load, normal use at 100%, and heavy use at 150%. Useful for planning worst-case and best-case battery life before a trip, event, or deployment — without running separate calculations.
The core formula for battery runtime is simple: hours = battery capacity (Wh) ÷ load (W). Because watt-hours already factor in voltage, this works for any battery chemistry. If you only know mAh and voltage, convert first: Wh = mAh × V ÷ 1000. A 4000 mAh phone battery at 3.7 V stores 14.8 Wh. Running a 1.5 W load gives 14.8 ÷ 1.5 = 9.9 hours in theory. In practice, multiply by an efficiency factor (85% is the standard for lithium-ion) to get a realistic estimate of about 8.4 hours.
Comparing two batteries purely by mAh only works when both run at the same voltage. A 5000 mAh phone battery at 3.87 V stores 19.35 Wh. A 3000 mAh laptop cell at 11.4 V stores 34.2 Wh — nearly twice the energy despite being fewer milliamp-hours. Always use watt-hours when comparing batteries across different device types. Airlines also cap carry-on lithium batteries at 100 Wh, so knowing the Wh value matters for travel planning too.
Lithium-ion charging happens in two phases. The first is constant-current (CC): the charger pushes the rated current until the battery reaches its maximum voltage (4.2 V for standard Li-ion cells). This phase is the fast part. The second is constant-voltage (CV): the voltage holds steady and current tapers off slowly as the cell fills the last 20% of capacity. Total charge time is typically 1.2× the CC-only time. A 4000 mAh battery charged at 2000 mA takes 2 hours in CC phase, then another ~24 minutes in the CV phase — about 2.4 hours total.
Lithium-ion batteries lose roughly 2–4% of capacity per 100 full charge cycles. A phone battery that started at 4000 mAh may hold only 3200 mAh (80% health) after 300–500 cycles. That 20% capacity loss means 20% shorter runtime on every charge. Most manufacturers recommend replacing a battery when health falls below 80%. Use the Battery Health tab to track degradation using the original rated capacity, current measured capacity, and cycle count — the tool shows health percentage, lost mAh, and estimated cycles remaining.
This Battery Life Calculator tool is a helpful online calculator to estimate how long a battery can power a device based on current and capacity. It is useful for electronics projects and daily usage planning. You can also combine it with Engineering Unit Conversion online, use Download Time Calculator online, and Programmer Calculator tool for better technical calculations.
Short, clear answers about battery life, mAh, Wh, charge time, and more.
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