Water Weight Converter • Temperature-aware

Convert water volume ⇄ weight with real-world density

Liters, mL, cups, fl oz, US/Imperial gallons ⇄ kilograms, grams, pounds, ounces. Uses temperature-based density (Kell) — defaults to 20 °C.

At 20 °C

~0.9982 kg/L

1 US gallon

3.78541 L

1 cup

240 mL

Convert water between volume and weight using temperature-aware density. Click Open Converter to start.

Water Weight Converter • Temperature-aware

Convert water volume ⇄ weight with real-world density

Liters, mL, cups, fl oz, US/Imperial gallons ⇄ kilograms, grams, pounds, ounces. Uses temperature-based density (Kell) — defaults to 20 °C.

Enter your value

Density at 20.0°C: 0.9982 kg/L

Note: freshwater, sea-level assumptions. For lab-grade work, use calibrated density tables.

Volume (primary)
—
Liters / mL / cups / fl oz
Weight (derived)
—
kg / g / lb / oz
Liters
—
Milliliters
—
Cups (240 mL)
—
US fl oz
—
US Gallons
—
Imperial Gallons
—
Kilograms
—
Grams
—
Pounds
—
Ounces
—
How it works: mass = volume × density. Water density varies with temperature (~1.000 kg/L @ 4 °C; ~0.998 kg/L @ 20 °C). We estimate density via the Kell polynomial.

Convert water between volume and weight using temperature-aware density. Enter a value, choose a unit, set the water temperature, and get liters, gallons, kilograms, and more.

Quick presets & unit reference

Load the converter with a single tap. Presets include the correct temperature so your density is realistic.

Popular presets

1 Liter of water

Room temperature density (~20 °C)

Volume → WeightL ⇄ kg
Edit

1 US gallon

Kitchen/room temp (~20 °C)

Volume → Weightgal ⇄ lb
Edit

5 lb of water

Cold water (~4 °C, near max density)

Weight → Volumelb ⇄ L
Edit

500 mL bottle

Warm room (~25 °C)

Volume → WeightmL ⇄ g
Edit

Choose a quick preset like one liter or one US gallon. The page will open the converter pre-filled with realistic temperature and units.

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Why temperature matters

Water density peaks near 4 °C and decreases as it warms. That shifts how liters convert to kilograms (and vice versa).

Set a temperature

ρ(20.0°C) ≈ 0.9982 kg/L

At this temperature, 1 L of water weighs about 0.9982 kg.

Freshwater Sea-level pressure Kell density
Read FAQs

Water density vs temperature

Peak density ~4 °C
Density decreases as water warms. Our converter uses this curve so volume ⇄ weight stays realistic.

Water is densest near four degrees Celsius and gets less dense as it warms. The converter adjusts liters to kilograms using this density curve.

Start converting

Pick a mode below. We’ll pre-fill the converter and scroll you to it.

Tip: your selection updates the URL hash (#wwc=…) and fills the tool automatically. Read FAQs

Choose a preset like one liter or one kilogram. The converter below will auto-fill and calculate using your selected temperature.

FAQs

Short answers to the questions people ask most about converting water volume and weight.

Density Does temperature really change water’s weight per liter?
Yes. Water is densest near ~4 °C (~1.000 kg/L) and slightly less dense at room temperature (~0.998 kg/L at 20 °C). The tool adjusts conversions using a temperature-based density curve so 1 L ⇄ kg stays realistic.
Accuracy How accurate is this converter?
It uses a standard freshwater density approximation (Kell-style) for 0–100 °C at sea-level pressure. It’s suitable for education and everyday estimates, not lab-grade measurements.
Units Do ounces mean the same thing in volume and weight?
No. A fluid ounce (fl oz) is volume; an ounce (oz) is weight. This page shows both where relevant and labels them clearly.
Gallons US vs Imperial gallon — which should I pick?
In the US, use the US gallon (3.78541 L). The Imperial gallon (4.54609 L) appears in some Commonwealth contexts (e.g., older UK references).
Settings What temperature should I use?
Use the temperature the water actually is. For kitchen tap or room temp, 20–25 °C is common. For refrigerated water, 4–8 °C is typical.
Environment Does altitude or salinity matter?
Yes, both can change density slightly. This tool assumes freshwater at sea-level pressure. For seawater or high-altitude precision, specialized tables or lab methods are recommended.
Sharing Can I share my results?
Yes. Use Share link to copy a URL with your inputs in the hash (#wwc=…). Anyone with the link can open the page pre-filled and see the same results.
Printing Can I print or save a PDF?
Use the Print / PDF button in the converter. The layout is print-optimized and hides interactive controls in the PDF.
Back to Converter See Presets

Frequently asked questions about converting water volume and weight: temperature, accuracy, unit differences, and sharing results.

Worked examples

One-click presets plus the exact steps you’d follow in the converter.

1 L → kg (20 °C)

Volume → WeightL ⇄ kg
  1. Set Value to 1 and Unit to Liters (L).
  2. Set Temperature to 20 °C (room temp).
  3. Click Convert — 1 L ≈ 0.9982 kg.
Edit

1 US gal → lb (20 °C)

Volume → Weightgal ⇄ lb
  1. Choose US Gallons and enter 1.
  2. Set temperature to 20 °C.
  3. Convert — 1 US gal (3.78541 L) ≈ ~8.34 lb at 20 °C.
Edit

5 lb → L (4 °C)

Weight → Volumelb ⇄ L
  1. Select lb and enter 5.
  2. Set temperature to 4 °C (near max density).
  3. Convert — volume will be slightly less than at 20 °C.
Edit

500 mL → oz (25 °C)

Volume → WeightmL ⇄ oz
  1. Pick mL and enter 500.
  2. Set temperature to 25 °C.
  3. Convert — you’ll see ounces (oz) in the results.
Edit

All examples assume freshwater at sea-level pressure.

About & attribution

How this tool works, its assumptions, and what we optimized for.

Version: v1.0.0 Last updated: September 15, 2025

Method & assumptions

  • Physics: mass = volume × density (freshwater).
  • Density model: temperature-aware empirical curve (0–100 °C) approximating the classical freshwater trend with peak near ~4 °C.
  • Units: US gal = 3.78541 L, Imp gal = 4.54609 L, cup = 240 mL, US fl oz = 29.5735 mL, 1 kg = 2.20462 lb, 1 oz (wt) = 28.3495 g.
  • Precision: results shown with sensible significant digits; extreme magnitudes auto-switch to scientific notation.
  • Scope: freshwater at ~sea-level pressure; salinity/altitude not modeled.
Client-side only No cookies for results Accessible labels Mobile-first

Changelog & credits

  • v1.0.0: Temperature slider with live density; presets; shareable hash; print-ready layout; examples & FAQs.
  • Design system: white/black/blue palette with Poppins, high-contrast focus rings, and keyboard-first navigation.
  • Attribution: Unit definitions follow standard SI/US customary values; density curve follows well-known freshwater behavior used in educational contexts.

Educational tool only — not a substitute for laboratory measurements.

About this converter: method, assumptions, version, and changelog.