Primary formula
Wh = voltage x Ah. Usable Wh = nominal Wh x usable fraction x efficiency x reserve fraction. Runtime = usable Wh / load W.
Everyday Life calculator
Battery Life Calculator
Estimate battery runtime from capacity, voltage, load, usable capacity, efficiency, reserve and optional duty cycle.
Last reviewed: July 7, 2026Everyday Life utility engine v1.0.0: costs, fuel, tariffs, data usage and battery runtime
Everyday Life calculator
Battery Life Calculator
Enter your values and calculate locally. Currency changes display only and does not convert values.
Mode
Optional load rows
Enter your values and choose Calculate to show the result, visual breakdown and detailed table.
Formula and assumptions
Input assumptions
Charging time is not calculated in this phase. Peukert mode is labelled as a lead-acid-style estimate. Current-mode inputs require compatible current units or voltage for watt output.
Precision note
Decimal.js is used for money, rate, tariff, fuel, data and battery arithmetic. Results are rounded only for display.
Everyday Life calculation flow
Validate
Check required fields, positive quantities, percentages, rows and divisor safety.
Normalize
Convert compatible distance, volume, fuel economy, energy and data units through the central registry.
Calculate
Apply the selected formula, tariff, split, projection or runtime model with Decimal.js precision.
Explain
Show result cards, visual breakdown, detailed rows, warnings, export and related tools.
What the Battery Life Calculator does
The Battery Life Calculator helps with estimating battery runtime from capacity and electrical load. It is built for practical estimates from values you enter, not for pulling live prices, tariffs, fares or provider records.
Results are calculated locally in the browser session and are intended to make assumptions visible before you use the number for planning.
How to use the Battery Life Calculator
Choose the mode that matches your question, enter the required values, then select Calculate. Reset restores the page defaults and hides the current result.
After calculation, review the primary result, supporting cards, visual breakdown, detailed rows and warnings before using the estimate.
Input definitions
Inputs are labelled by cost, unit, rate or frequency. Optional fields default to zero unless the field represents a required amount such as distance, usage, capacity or load.
Use the units shown beside each field. When the page supports multiple unit systems, values are normalized through the central NexaCalc conversion definitions before formula logic runs.
Formula or algorithm
Wh = voltage x Ah. Usable Wh = nominal Wh x usable fraction x efficiency x reserve fraction. Runtime = usable Wh / load W.
Decimal.js is used for arithmetic that involves money, rates, usage, tariffs, fuel, data or battery quantities. Display rounding happens after calculation.
Assumptions
The calculator uses these visible assumptions rather than hidden defaults.
- Charging time is not calculated in this phase.
- Peukert mode is labelled as a lead-acid-style estimate.
- Current-mode inputs require compatible current units or voltage for watt output.
Result interpretation
The headline result answers the main page question. Supporting rows show how the result was assembled so you can check each part of the estimate.
A result that looks precise is still an estimate when it depends on user-entered prices, rates, behaviour, tariff rules or device performance.
Unit and currency handling
Energy and power values use Wh/W runtime relationships and align with central conversion concepts.
Changing the currency label changes display only. It does not perform foreign-exchange conversion.
Step-by-step calculation
The engine validates required inputs, converts compatible units, calculates the base quantity, applies charges or rates, reconciles the final total and then formats the output.
If an impossible value would create a divide-by-zero, negative usage, NaN or Infinity result, the calculator blocks the result and shows a clear validation message.
Worked examples
12 V and 100 Ah gives 1200 Wh nominal energy.
With 80% usable capacity and 90% efficiency, usable energy is 864 Wh and a 100 W load runs about 8.64 hours.
3000 mAh at 200 mA gives 15 ideal hours and 13.5 hours at 90% efficiency.
Practical use cases
Use the Battery Life Calculator for quick planning, checking a spreadsheet, comparing simple scenarios, or explaining a household estimate to someone else.
For invoices, bills, contracts or safety-critical decisions, compare the result with the official provider, utility, manufacturer or governing standard.
Common mistakes
These mistakes are common when people use quick everyday calculators.
- Confusing mAh with Wh without voltage.
- Ignoring usable capacity and converter losses.
- Applying Peukert silently to lithium batteries.
Limitations
The tool intentionally stays deterministic and does not fetch provider-specific or location-specific data.
- No chemistry-specific discharge curve.
- No charging-time result.
- No manufacturer warranty prediction.
Privacy note
Inputs are calculated in-session. NexaCalc does not require an account for these tools and does not upload bills, participant names, travel plans, meter readings, browsing activity, mobile usage or battery details.
Frequently asked questions
What is the Battery Life Calculator?
It is a NexaCalc tool for estimating battery runtime from capacity and electrical load from values you enter.
Does this calculator use live prices or tariffs?
No. It calculates from user-entered rates, costs and assumptions only.
Does changing currency convert money?
No. The currency selector changes display formatting only and does not fetch exchange rates.
Are results exact?
Formula arithmetic is deterministic, but real-world outcomes can differ because rates, usage and behaviour can change.
Why is the result hidden before Calculate?
NexaCalc avoids fake default results. The result and visual appear only after a valid calculation.
Can I copy or share a result?
Yes. Result controls let you copy, print, share or use social-friendly copy fallbacks from the browser.
Are my inputs stored?
No. These tools calculate locally in the browser session and do not require an account.
What should I do with validation errors?
Check missing required fields, negative values, zero divisors, invalid percentages and incomplete rows.
Why does the page show warnings?
Warnings identify estimate limits such as local tariff rules, rounded values, provider measurement differences or user-entered assumptions.
Can this replace an official bill or quote?
No. Use the result as a planning estimate and verify important costs with the provider, bill, tariff, invoice or manufacturer data.
References
- U.S. Department of Energy, Energy Saver guidance on estimating energy use. Source.
- NIST Special Publication 811, Guide for the Use of the International System of Units. Source.
- BIPM, The International System of Units SI Brochure. Source.
- IEC, Binary prefixes for bytes and digital storage units. Source.
- U.S. EPA and DOE FuelEconomy.gov, fuel economy concepts and measurement context. Source.
Everyday Life Phase 1 references and user-entered estimate conventions reviewed on July 7, 2026.
Educational disclaimer
This calculator provides mathematical results from the values, conventions and methods you enter. Verify important academic, engineering or professional work independently.