Building Height Calculator

1) Trig with top and base angles

H = D × (tan(θ) − tan(α)) + hᵢ

Use when you can measure both the top and the base angles from the same point. This corrects for sloping ground without needing a separate elevation offset.

2) Trig with a single angle and base offset

H = D × tan(θ) + hᵢ − Δb

Use when the base is near level with your station, or when you know the base elevation difference Δb (positive if the base is higher than you).

3) Shadow ratio

H = Lb × (Hr / Lr) + f

Measure the building shadow length Lb and a reference object of known height Hr with shadow length Lr at the same time. Add foundation/plinth correction f as needed.

4) Floors and add-ons

H = N × h_ff + r + f + p

Where N is floor count, h_ff is floor-to-floor height, r is roof/mechanical allowance, f is plinth/foundation, and p is parapet/coping height.

1. Select a method that matches your available measurements.
2. Choose meters or feet, then enter the required inputs.
3. Press Calculate Height to see the result above the form.
4. Review the inputs and steps to validate field readings.
5. Use Download CSV or Download PDF for records.

• Keep angles within a realistic range to reduce error.
• Re-measure distance and angles if results look unusual.
• For tall buildings, take multiple readings and compare.

1) Why building height matters

Building height influences zoning limits, fire access, lift design, wind exposure, and façade maintenance planning. On projects, teams often need fast field estimates for due diligence, retrofit surveys, and progress checks. This calculator supports four common approaches, helping you document assumptions and reduce rework.

2) Trig method with top and base angles

When you can sight both the top and the base from one station, the height is found using H = D × (tan(θ) − tan(α)) + hᵢ. Here, D is horizontal distance, θ is the top angle, α is the base angle, and hᵢ is instrument height. This method handles sloping ground without a separate elevation survey.

3) Trig method with offset

If the base angle is not observable, use H = D × tan(θ) + hᵢ − Δb, where Δb is the base elevation offset relative to your station. Enter Δb as positive when the base is higher than your position. This approach is practical on flat sites, courtyards, or where the base line is obstructed.

4) Shadow ratio for quick daylight checks

On sunny days, shadow scaling can be reliable: H = Lb × (Hr / Lr) + f. Measure the building shadow length Lb and a reference object of known height Hr with its shadow length Lr at the same time. Keep the ground level, ensure both shadows lie on similar surfaces, and add f for plinth or grade corrections.

5) Floors and add-ons for early-stage estimates

For preliminary design, height can be approximated from storey count: H = N × h_ff + r + f + p. Typical floor-to-floor heights are often 2.8–3.4 m for residential and 3.6–4.2 m for offices, while mechanical screens and parapets commonly add 0.5–2.0 m depending on equipment and detailing.

6) Accuracy, uncertainty, and repeat readings

Small angle errors amplify height error at long distances. For example, at D = 40 m, a 1° error near 30° changes tan(θ) by roughly 0.03, shifting height by about 1.2 m. Take at least three readings, average them, and re-check distance. Avoid angles above 60° when possible by stepping farther back.

7) Unit handling and field documentation

Choose meters or feet before entering values so all lengths remain consistent. Record the method, the station location, and any offsets used. Exporting CSV supports logs and spreadsheets, while PDF output is useful for attaching to site reports, inspection notes, and permit documentation.

8) Practical safety and workflow tips

Use safe observation points away from traffic and hazards, and avoid stepping into the roadway for a better sightline. Confirm that “horizontal distance” is truly horizontal, not sloped tape distance. When obstacles block the base, prefer the offset method or shadow ratio, then compare results for a sanity check.

1) Which method should I choose first?

Start with the trig method using top and base angles when you can see both points. It corrects for slope naturally. If the base is hidden, use the offset method or shadow ratio, then compare with the floors estimate.

2) Do I need a professional survey instrument?

No. A clinometer or a phone inclinometer can work for approximate heights. For higher accuracy, use a laser rangefinder for distance and take multiple angle readings. Document equipment and conditions in your report.

3) What does base elevation offset mean?

Base offset is the vertical difference between the building base and your standing point. Enter it as positive when the base is higher than you, and negative when the base is lower. This corrects the single-angle trig estimate.

4) Why does my result seem too high or too low?

Check that distance is horizontal, angles are in degrees, and the correct sign is used for the base angle or offset. Re-measure at a longer distance to reduce steep angles, and confirm instrument height is included.

5) How can I improve accuracy on tall buildings?

Increase the observation distance so the top angle stays moderate, repeat measurements, and average results. Use a laser rangefinder for D and avoid readings in strong heat shimmer or heavy wind, which can affect sighting stability.

6) When is the shadow method unreliable?

It becomes unreliable on uneven ground, when shadows fall on different slopes or surfaces, or when clouds change sunlight between measurements. Ensure both shadows are measured at the same time and that the reference object is truly vertical.

7) What should I include in a site record?

Note the method used, date and time, unit system, station location, distance measurement approach, instrument height, and any offsets or add-ons. Attach the CSV or PDF output and keep photos of the measurement setup if possible.