Battery Backup Time Calculator
Estimate UPS / battery runtime for a load.
Instant · runs in your browserAbout the Battery Backup Time Calculator
Planning for load shedding? Enter your battery's capacity (Ah) and voltage, the number of batteries and the load in watts, and get an estimate of how long your UPS or inverter will keep things running.
Formula
Backup time (h) ≈ (Ah × V × number of batteries × efficiency) ÷ load (W). A 150 Ah, 12 V battery running 200 W at 80% efficiency lasts about 7 hours in theory.
Good to know
Lead-acid batteries shouldn't be drained fully; usable capacity is often only about half of the rating, and older batteries hold less.
بیٹری بیک اپ ٹائم
لوڈ شیڈنگ کے لیے: بیٹری کی گنجائش (Ah)، وولٹیج، تعداد اور لوڈ (واٹ) درج کریں اور جانیں کہ یو پی ایس کتنی دیر چلے گا۔
- لیڈ ایسڈ بیٹری کو مکمل خالی نہ کریں
- پرانی بیٹری کم بیک اپ دیتی ہے
How to use Battery Backup Time Calculator
- Enter your values. Units and defaults are shown beside each field.
- Press Calculate (results also update as you type once calculated).
- Read the result and the step-by-step breakdown with the formula used.
- Copy the result or reset to start again.
Frequently asked questions
How accurate is this calculator?
Calculations use the standard formulas shown on the page, computed in full precision and rounded only for display. The result is only as accurate as the inputs and assumptions listed.
Can I use this for engineering design?
No. These are rough quantity estimates using the assumptions shown (wastage, densities, mix ratios). Get structural and electrical work designed and approved by a qualified engineer.
Is it free?
Yes. All tools are free to use without an account.