# How to Choose a Filling Machine | AXTRA > Learn how to choose a liquid filling machine: volumetric, gravity and piston filling compared by viscosity, accuracy and best use case. - Source page: https://www.axtra.com/how-to-choose-a-filling-machine/ - Language: English (en) - Last updated: 2026-09-23 - Publisher: AXTRA S.r.l. - https://www.axtra.com/ - Other languages: [de](https://www.axtra.com/de/wie-sie-die-richtige-abfuellmaschine-waehlen-volumetrisch-schwerkraft-und-kolben-im-vergleich.md), [es](https://www.axtra.com/es/como-elegir-una-maquina-de-llenado-comparacion-entre-volumetrica-gravedad-y-piston.md), [fr](https://www.axtra.com/fr/comment-choisir-une-remplisseuse-comparaison-volumetrique-gravitaire-et-a-piston.md), [it](https://www.axtra.com/it/come-scegliere-una-macchina-riempitrice-confronto-tra-volumetrica-gravita-e-pistone.md), [pt-br](https://www.axtra.com/pt-br/como-escolher-uma-maquina-de-enchimento-comparacao-entre-volumetrica-gravidade-e-pistao.md), [ru](https://www.axtra.com/ru/%d0%ba%d0%b0%d0%ba-%d0%b2%d1%8b%d0%b1%d1%80%d0%b0%d1%82%d1%8c-%d1%80%d0%b0%d0%b7%d0%bb%d0%b8%d0%b2%d0%be%d1%87%d0%bd%d1%83%d1%8e-%d0%bc%d0%b0%d1%88%d0%b8%d0%bd%d1%83-%d1%81%d1%80%d0%b0%d0%b2%d0%bd.md) --- ## How to Choose a Filling Machine: Volumetric, Gravity and Piston Compared Knowing how to choose a filling machine starts with a question most buyers skip past too quickly: what, exactly, does the product do when it moves? Thin and free-flowing, thick and slow, or somewhere in between — the answer determines which filling technology will actually work, before speed, footprint or budget even enter the conversation. This guide compares the three most common filling technologies — volumetric, gravity and piston — to help match one to your product. ## Start with Product Viscosity Water-thin liquids, medium-viscosity products and thick or dense products each behave differently as they move through a filling head, and a technology optimised for one will underperform on another. Describing the product honestly — not aspirationally — is the single most useful input into choosing a filling machine, more useful at this stage than comparing brochures. ## Gravity Filling Gravity fillers let the product’s own weight do the work, flowing from a reservoir into the bottle through a valve. They are mechanically simple, cost-effective, and well suited to thin, free-flowing liquids such as water, still wine and light oils. Accuracy is typically in the range of ±1-2%, which is adequate for many products but not for those requiring tight fill-level tolerance. Gravity systems struggle as viscosity increases, since flow becomes slower and less predictable. ## Volumetric Filling [Volumetric fillers](https://www.axtra.com/still-liquids-filling-machine/) dispense a fixed, pre-set volume using metering technology rather than relying on gravity alone, achieving accuracy around ±0.5% across a wider range of viscosities than gravity systems. This makes volumetric filling a strong general-purpose choice when a line needs to run several product variants without swapping the entire filling technology between them. ## Piston Filling Piston, or positive-displacement, fillers use a piston to draw product from a reservoir and dispense an exact volume into each container. This method handles [medium-viscosity products](https://www.axtra.com/semi-viscous-liquids-filling-machine/) — creams, sauces, some personal care formulations — that gravity and standard volumetric systems cannot move reliably, typically achieving ±0.5-1% accuracy. Piston fillers are usually the right answer whenever “thick” is an honest description of the product. ## Quick Comparison - Gravity: best for thin liquids, ±1-2% accuracy, lowest complexity and cost. - Volumetric: best for a broad range of viscosities, around ±0.5% accuracy, strong general-purpose choice. - Piston: best for medium-viscosity and dense products, ±0.5-1% accuracy, required where gravity and volumetric systems fail to fill reliably. ## Beyond the Filling Technology Itself Once the core technology is right, production speed, changeover time between formats, and integration with the rest of the line — [capping](https://www.axtra.com/tag/capping-machines/), [labelling](https://www.axtra.com/tag/labelling-machines/), conveying — determine how well the filler performs in practice, not just on a spec sheet. AXTRA designs [filling machines](https://www.axtra.com/liquid-filling-machines-guide/) matched to product viscosity and required accuracy as part of a full modular line. [Contact AXTRA](https://www.axtra.com/contacts/) to discuss which filling technology fits your product. Product viscosity, the starting point for this decision, is explained in more depth on [Wikipedia](https://en.wikipedia.org/wiki/Viscosity). September 29, 2026 ### [Filling Accuracy Explained: What +/-0.5% Really Means for Your Line](https://www.axtra.com/filling-machine-accuracy-explained/) Filling machine accuracy is usually expressed as a small percentage — ±0.5%, ±1%, ±2% — and it’s easy to skim past those numbers without realising Read more » ### [How to Choose a Filling Machine: Volumetric, Gravity and Piston Compared](https://www.axtra.com/how-to-choose-a-filling-machine/) Knowing how to choose a filling machine starts with a question most buyers skip past too quickly: what, exactly, does the product do when it [previousFilling Accuracy Explained: What +/-0.5% Really Means for Your Line](https://www.axtra.com/filling-machine-accuracy-explained/) [nextLiquid Filling Machines: The Complete Guide](https://www.axtra.com/liquid-filling-machines-guide/) #### Contact us ## From empty container to finished product. --- Markdown version generated by LABOOM SEO/GEO Manager for AI agents. The HTML page above is the authoritative source.