Agarose gel percentage calculator & table

Maintained by the Talindrew team · Last updated September 26, 2026

Agarose percentage sets the sieving range of a gel: low percentages resolve large DNA, high percentages resolve small. Standard ranges run from 0.5% (1–30 kb) through 1% (0.5–10 kb), the everyday default, to 2% (50 bp–2 kb). Enter your smallest and largest fragments and the guide picks the tightest gel that resolves both.

Smallest fragment

Largest fragment

Result

Recommended gel1.5% agarose

0.5% gel resolves1–30kb

0.7% gel resolves0.8–12kb

1% gel resolves0.5–10kb

1.2% gel resolves0.4–7kb

1.5% gel resolves0.2–3kb

2% gel resolves0.05–2kb

Ranges per Sambrook & Russell and vendor electrophoresis guides. For ranges no single gel covers, run two gels or a gradient; below ~100 bp consider polyacrylamide.

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What it looks like

Schematic gel: band positions assume distance travelled is linear in log(size) across the gel's resolving range, with fragments outside it compressed near the wells or the dye front. Real mobility also depends on buffer, voltage and DNA form (supercoiled plasmid runs differently).

Formula

0.5% → 1–30 kb · 0.7% → 0.8–12 kb · 1.0% → 0.5–10 kb · 1.2% → 0.4–7 kb · 1.5% → 0.2–3 kb · 2.0% → 0.05–2 kb

Source: Sambrook & Russell, Molecular Cloning; vendor electrophoresis guides

Worked example

Given: Diagnostic digest expected to give 0.5 kb and 2 kb bands

1.Both fragments must fall inside one gel's range.
2.1.5% resolves 0.2–3 kb: covers 0.5 and 2 kb with good separation in the small range.
3.1.0% would also cover it but compresses the 0.5 kb end; the guide picks the tighter 1.5%.

Pour a 1.5% agarose gel

How the calculation flows

The expected fragment range is matched against each percentage's resolution window; the tightest covering gel maximises band separation.

Units & constants

Everyday default	1%: resolves 0.5–10 kb, covers most cloning checks
Below ~100 bp	Use 2.5–3% agarose or polyacrylamide
Above ~30 kb	Pulsed-field electrophoresis territory
High-% pouring tip	≥ 2% gels need slow, complete melting to avoid lensing
Verify in-app	Talindrew's gel simulator predicts band positions for your actual digest
Price	Free

Why does percentage change what a gel resolves?

Agarose forms a pore network that DNA snakes through; pore size shrinks as percentage rises. Large molecules barely enter a tight matrix (they compress at the well in 2%), while small fragments run unretarded through a loose one (they blur at the front in 0.5%). Matching pore size to fragment size is all this choice is.

How do you decide when bands are close together?

Separation matters most where your bands are closest. If you must distinguish 900 bp from 1,100 bp, choose the highest percentage whose range still includes both (1.5%), run longer at lower voltage, and use a ladder with rungs bracketing the gap. Better still, simulate the digest first: Talindrew's gel simulator shows whether the two bands will visibly separate before you pour anything.

Frequently asked questions

1.5–2%. At 1% a 300 bp band runs near the dye front with little resolution; 2% places it mid-gel where 50–100 bp differences are visible.

For checks of fragments between 0.5 and 10 kb, yes, that is why it is the default. You lose real information outside that window: sub-500 bp bands compress together and > 10 kb fragments crowd the well.

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