Parts per trillion is the unit of the almost-undetectable — the scale where a single drop in twenty Olympic swimming pools still counts as a measurable concentration. Getting there from parts per million takes a multiplication by 1,000,000, a factor so large it deserves a pause: 1 ppm is a million ppt. Enter 1 in the PPM box and the PPT readout shows 1,000,000, with the PPB box at 1,000 as the middle rung. The schema's second example is the instructive one — 0.001 ppm becomes 1,000 ppt — showing how a whisper-quiet ppm reading turns into a comfortable whole number in ppt. This is the native language of dioxin testing, hormone-disruption research, and ultra-trace metal analysis, where instruments count molecules and regulators set limits in the low ppt. The percent box, dividing ppm by 10,000, sits at the far other end of the page at 0.0000001%, a number that demonstrates exactly why ppt exists. When a study reports 5 ppt of something in drinking water, that is 0.000005 ppm — now you can translate it.

With the pre-filled defaults — PPM 1 — the PPM to PPT returns PPT 1,000,000, PPB 1,000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.