Why does the loading buffer need to be diluted to 1x?

Loading dyes are sold concentrated, typically 6x, to save freezer space. The glycerol, tracking dyes, and any SDS or EDTA only work correctly at the final 1x strength, so the buffer volume is fixed at the total well volume divided by its concentration factor.

What if the requested DNA mass needs more sample than the well holds?

The tool caps the sample volume to the space left after the buffer and reports the actual mass you can load. To reach your target mass you must either concentrate the sample or pour a thicker gel with larger wells.

How much DNA should I load per lane?

For a standard stained agarose gel, 100 to 500 nanograms per band gives a clear, sharp signal without overloading. Overloaded lanes smear and distort migration, while too little DNA is hard to photograph.

Does the water or TE volume matter?

Yes. When the mass-limited sample volume is smaller than the available space, topping up with water or TE keeps the total well volume constant so every lane runs at the same height and the dye stays at 1x.

Can I use this for RNA or protein gels?

The volume math is the same for any sample where you mix concentrated loading buffer with a sample to a fixed well volume. Only the recommended mass per lane and buffer chemistry differ, so adjust the target mass accordingly.

Gel Loading Volume Calculator

Setting up an agarose gel means combining your DNA sample with a concentrated loading dye so the dye ends up at 1x and the whole mix fits your well. This calculator does that arithmetic for you and tells you exactly how many microlitres of sample, buffer, and top-up water to pipette per lane.

How it works

The recipe is built from four numbers. First, the buffer volume is fixed by its concentration: a 6x dye in a 12 µL well needs 12 / 6 = 2 µL of buffer to reach 1x. That leaves the remaining 10 µL for sample and water.

The sample volume needed to deliver your target mass is desired mass / sample concentration. For 200 ng from a 50 ng/µL stock that is 4 µL. The rest of the sample space, here 6 µL, is filled with water or TE so the total stays at 12 µL and the dye stays correctly diluted.

Worked example

With a 12 µL well, 6x dye, a 50 ng/µL sample, and a 200 ng target you pipette 2 µL buffer, 4 µL sample, and 6 µL water. If your sample were only 10 ng/µL, the 20 µL of sample needed for 200 ng would not fit, so the tool caps the sample at 10 µL and reports the 100 ng you can actually load.

Tips

Always read your sample concentration freshly rather than assuming the elution value. Avoid overloading: a smeared, fat band migrates abnormally and ruins size estimation. If you routinely cannot reach your target mass, concentrate samples by a quick spin-column step or cast a comb with deeper wells.