Time Unit Converter

Sampling intervals, dosing rates and hydraulic residence times are quoted in seconds on one control loop, minutes on a timer and days on a process report, while a year closes the plant-energy balance. This converter moves exactly between them with no approximation.

Convert time unit units

Value

From

Why time units collide

Process time stacks seconds, minutes, hours, days, weeks and years on base-60 and base-24 factors, and the year is the one non-uniform unit: this converter uses the Julian year of 365.25 days (31 557 600 s) for a consistent astronomical and engineering standard.

All factors are exact except the year, which is a defined convention. The converter is exact arithmetic, so the value you read matches the unit you selected without rounding.

Which unit where

Seconds and milliseconds rule control loops, sampling and response times; minutes and hours describe timers, dosing and batch steps; days and weeks are the process and reporting scale; years close energy and maintenance balances. Match the unit your spec writes in, then convert.

Complete conversion reference

Convert 1 unit to	s	min	h	day	week	ms	yr
1 s	1	0.0166667	0.000277778	1.15741e-05	1.65344e-06	1000	3.16881e-08
1 min	60	1	0.0166667	0.000694444	9.92063e-05	60000	1.90129e-06
1 h	3600	60	1	0.0416667	0.00595238	3.6e+06	0.000114077
1 day	86400	1440	24	1	0.142857	8.64e+07	0.00273785
1 week	604800	10080	168	7	1	6.048e+08	0.019165
1 ms	0.001	1.66667e-05	2.77778e-07	1.15741e-08	1.65344e-09	1	3.16881e-11
1 yr	3.15576e+07	525960	8766	365.25	52.1786	3.15576e+10	1

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Frequently asked

How many seconds in a day?

Exactly 86 400 s (24 × 3600). One week is 604 800 s and one hour is 3600 s. The converter applies these exact factors so residence and sampling times line up.

What is a year in seconds?

This converter uses the Julian year of 365.25 days = 31 557 600 s, the standard for engineering and astronomical time. Calendar years vary by leap days, so use this defined value for balances.

Why does residence time use days but control uses seconds?

Hydraulic and biological residence times are quoted in days or hours, while control loops and sampling run in seconds or minutes. Convert at the boundary so a rate or setpoint is consistent.

Is a millisecond the same as a second?

No. One millisecond is exactly 0.001 s (10⁻³ s). Response and sampling times in fast loops are often in ms; convert to seconds for any slower process calc.

This page performs exact unit arithmetic with no physical assumption beyond the stated reference (for example mH₂O assumes water near 4 °C, and pH follows its logarithmic definition). It is a working aid, not a substitute for the measurement method named in your permit.