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Loan Calculator
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UPS Runtime Calculator
Calculates how long a UPS or battery bank will carry a load, accounting for depth of discharge and inverter efficiency.
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In short
UPS Runtime Calculator is a free online tool on inputtesthub.com that calculates how long a UPS or battery bank will carry a load, accounting for depth of discharge and inverter efficiency. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.
How to use the UPS Runtime Calculator
- Enter your figures in the input fields.
- The result updates as you type, together with the full working.
- Check the breakdown table to see exactly how the number was reached.
About the UPS Runtime Calculator
The UPS Runtime Calculator calculates how long a UPS or battery bank will carry a load, accounting for depth of discharge and inverter efficiency. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- Sizing a UPS for a router and PC during load-shedding.
- Checking how long an existing bank will last.
- Comparing lead-acid against lithium for the same backup time.
Details
| Lead-acid safe DoD | 50% |
|---|---|
| LiFePO₄ safe DoD | 80–90% |
| Inverter efficiency | 80–90% |
| 100 Ah at 12 V | 1,200 Wh nominal, ~510 Wh usable |
The maths behind it
This tool uses Usable energy = Ah × V × batteries × depth of discharge × inverter efficiency. Runtime = usable energy ÷ load in watts. Every intermediate value is shown on screen, so the result can be checked by hand.
Depth of discharge is what people leave out, and it halves the answer. A lead-acid battery repeatedly taken below 50% loses most of its life in months. At high discharge rates a lead-acid bank also delivers noticeably less than its rated Ah.
Frequently asked questions
How long will a 100 Ah battery run a 300 W load?
About 1 hour 40 minutes on lead-acid — 1,200 Wh nominal, but only half is safely usable and the inverter loses 15% of that. Lithium at the same rating would give closer to 3 hours.
Why does my UPS last less than the calculation says?
Usually depth of discharge and battery age. A three-year-old lead-acid battery may hold 60–70% of its rated capacity, and taking it deeper to compensate accelerates the decline.
Do I need an account to use the UPS Runtime Calculator?
There is no cost and no cap. The UPS Runtime Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Can you see what I put into this utility?
No. The UPS Runtime Calculator runs entirely in your browser using JavaScript. Because the work happens locally, the utility also keeps working if your connection drops, and closing the tab is all it takes to discard everything.
What formula does the UPS Runtime Calculator use?
It uses Usable energy = Ah × V × batteries × depth of discharge × inverter efficiency. Runtime = usable energy ÷ load in watts. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What do people use the UPS Runtime Calculator for most?
Typical uses: sizing a UPS for a router and PC during load-shedding. Checking how long an existing bank will last. Comparing lead-acid against lithium for the same backup time. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What do people usually get wrong here?
Depth of discharge is what people leave out, and it halves the answer. A lead-acid battery repeatedly taken below 50% loses most of its life in months. At high discharge rates a lead-acid bank also delivers noticeably less than its rated Ah.
What are the key numbers for the UPS Runtime Calculator?
Lead-acid safe DoD is 50%. LiFePO₄ safe DoD is 80–90%. Inverter efficiency is 80–90%. These are printed on the page itself, so you do not have to take them on trust.
Can I rely on this for exact work?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.
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