Example preset
After making a selection, click "Apply" to reflect it in the input.
Inputs
In slope input mode, a straight line 1000 m ahead from the reference point (z0, T0) is displayed.
Results
Details
Temperature-depth graph
If you enter using the 2-point method, 2 points and a straight line will be displayed.
Alternative data for the graph is displayed in the following table.
Counting backwards (Advanced / Educational)
It is for rough estimation. If the assumptions of the input conditions do not match, please reconfirm with actual data.
Target heat flow → required gradient
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Target heat flow → required k
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Target gradient → required T2
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Assumptions & limits
- This is an approximation assuming only one-dimensional, steady state, and conduction.
- Depth z increases downwards (convention with z=0 at the surface).
- The heat flow rate q_up to be displayed is positive for "upwards toward the earth's surface", and the physical representation q_z=-k(dT/dz) is also shown.
- The formula uses Fourier's law q_z=-k(dT/dz) and also displays HFU (1 HFU = 41.84 mW/m²) from q_up(mW/m²) for reference.
- It does not include the effects of convection, groundwater flow, heat source distribution, unsteady state, or layered structure.
- Please do not use it as a basis for determining design/regulatory compliance; in practice, please follow local data and regulations.
How to use Geothermal gradient/heat flow (geothermal) calculation effectively
What this calculator does
This page is for estimating outcomes by changing inputs in one controlled workflow. The model keeps your focus on variables, not output shape. Start with stable assumptions, then test sensitivity by changing one key input at a time to observe directional impact.
Input meaning and unit policy
Each input has an expected unit and a typical range. For reliable interpretation, check whether you are using the same unit system, period, and base assumptions across all runs. Unit mismatch is the most common source of unexpected drift in numeric results.
Use-case sequence
A practical sequence is: first run with defaults, then create a baseline log, then run one alternative scenario, and finally compare only the changed output metric. This sequence reduces cognitive load and prevents false pattern recognition in early experiments.
Common mistakes to avoid
Avoid changing too many variables at once, mixing incompatible data sources, and interpreting a one-time output without checking robustness. A single contradictory input can flip conclusions, so keep each experiment minimal and document assumptions as part of your note.
Interpretation guidance
Review both magnitude and direction. Direction tells you whether a strategy moves outcomes in the desired direction, while magnitude helps you judge practicality. If both agree, you can proceed; if not, rebuild the baseline and verify constraints before deciding.
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FAQ
What is geothermal gradient?
It is a ratio that shows how much the temperature increases with depth. It can be estimated from the temperature difference and depth difference between two points.
What does heat flux mean?
It is how much heat flows per unit area (W/m²). This tool assumes only conduction and approximates by q≈k×(dT/dz).
The sign is difficult to understand
The physical display is q_z=-k dT/dz (z downward positive), and this tool also displays the upward heat flow q_up=k dT/dz for users.
What should I do first on this page?
Start with the minimum required inputs or the first action shown near the primary button. Keep optional settings at defaults for a baseline run, then change one setting at a time so you can explain what caused each output change.
Why does this page differ from another tool?
Different pages often use different defaults, units, rounding rules, or assumptions. Align those settings before comparing outputs. If differences remain, compare each intermediate step rather than only the final number.