Battery Energy Density Calculator
Find a battery's total stored energy plus its gravimetric (Wh/kg) and volumetric (Wh/L) energy density, compared against common chemistries.
🔋 What is Battery Energy Density?
Battery energy density measures how much energy a battery packs into a given mass or volume. Gravimetric energy density (Wh/kg) measures energy per unit weight, and volumetric energy density (Wh/L) measures energy per unit space, both computed from the battery's total stored energy.
Engineers and battery designers use this constantly, to compare different battery chemistries and cell formats when designing a product, to estimate how much a battery pack will weigh or how much space it will need for a target energy capacity, to benchmark a new cell design against commercial chemistries, and to understand the fundamental tradeoffs between energy density, cost, safety, and lifespan.
A common misconception is that a bigger amp-hour rating always means a denser, better battery. It doesn't, a battery with high capacity but also high mass and volume can have low energy density, energy density is specifically about energy per unit weight or space, not raw capacity alone.
This calculator computes total stored energy, gravimetric density, and volumetric density from your voltage, capacity, mass, and volume inputs, then compares your result against typical figures for lead-acid, NiMH, LFP, Li-ion, and solid-state lithium chemistries.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — 18650 Li-ion Cell
V=3.7 V, Ah=3, m=0.045 kg, vol=0.018 L
Example 2 — Lead-Acid Car Battery
V=12 V, Ah=50, m=14 kg, vol=8 L
Example 3 — LiFePO4 Pack
V=3.2 V, Ah=100, m=2.5 kg, vol=0.9 L
❓ Frequently Asked Questions
🔗 Related Calculators
What is battery energy density?
Battery energy density measures how much energy a battery stores relative to its size. Gravimetric energy density (Wh/kg) measures energy per unit mass, while volumetric energy density (Wh/L) measures energy per unit volume, both are computed from the battery's total stored energy in watt-hours.
How do you calculate total energy stored in a battery?
Total energy in watt-hours equals nominal voltage multiplied by capacity in amp-hours: E(Wh) = V x Ah. For example, a 3.7V, 3Ah cell stores 3.7 x 3 = 11.1 Wh of energy.
What is the difference between gravimetric and volumetric energy density?
Gravimetric energy density (Wh/kg) is total energy divided by mass, it matters most when weight is the constraint, like in aircraft or handheld devices. Volumetric energy density (Wh/L) is total energy divided by volume, it matters most when space is the constraint, like compact consumer electronics.
Why does lithium-ion have higher energy density than lead-acid?
Lithium is the lightest metal and has a highly negative electrode potential, letting lithium-ion cells store more energy per unit mass and volume than heavier lead-based or nickel-based chemistries. Lead-acid batteries use much heavier lead electrodes, which caps their achievable energy density.
What is a typical energy density for a phone or laptop battery?
Consumer lithium-ion cells (NMC or LCO chemistry) typically achieve 200 to 260 Wh/kg and 550 to 750 Wh/L at the cell level, which is why lithium-ion dominates portable electronics where both weight and size matter.
Why is LiFePO4 (LFP) lower energy density than other lithium-ion chemistries?
LiFePO4 cells trade some energy density (typically 90 to 160 Wh/kg) for better thermal stability, longer cycle life, and lower cost, since iron phosphate is more thermally stable but stores somewhat less energy per unit mass than nickel or cobalt-based cathodes.
Does higher energy density always mean a better battery?
No, energy density is only one factor. Power density (how fast energy can be delivered), cycle life, cost, safety, and operating temperature range all matter, which is why lead-acid, NiMH, and different lithium chemistries all remain in use despite lower energy density than the newest lithium-ion cells.
What units does this calculator use?
Voltage is entered in volts (V), capacity in amp-hours (Ah), mass in kilograms (kg), and volume in liters (L). Output total energy is in watt-hours (Wh), gravimetric density in Wh/kg, and volumetric density in Wh/L.
Does this calculator account for voltage sag under load?
No, this calculator uses the simple ideal formula E = V x Ah, assuming constant nominal voltage throughout discharge. Real batteries show voltage sag, especially at high discharge rates, so actual delivered energy under load is typically somewhat lower than this calculated value.
How does pack-level energy density compare to cell-level energy density?
A finished battery pack always has lower energy density than its individual cells, because the pack adds casing, wiring, battery management electronics, and often cooling systems that add mass and volume without adding stored energy. Datasheet chemistry figures are almost always cell-level, not pack-level.